International Units of SI

SCIENCE

INTERNATIONAL UNITS OF SI

7 BASE & 22 DERIVED UNITS

INTERNATIONAL UNITS OF SI

BASE UNITS

BASE · DERIVED
DECIMAL · BINARY · CONVERSION

BASE UNITS

Ampere

Ampere, A

SI Base Unit

Electric Current, I

SI Base Quantity

This unit of electric current (1 amp) is the flow capacity of the electric charge in one coulomb over a duration of one second. One coulomb is equivalent to the charge of 6.242×10¹⁸ electrons.

Formally, as defined in 2014:
“The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1m apart in vacuum, would produce between these conductors a force equal to 2 × 10⁻⁷ newton per metre of length.”

Proposed:
“The ampere, A, is the unit of electric current; its magnitude is set by fixing the numerical value of the elementary charge to be equal to exactly 1.602 17X × 10⁻¹⁹ when it is expressed in the unit A·s, which is equal to C.”

Discovered by André-Marie Ampère, 1820

Ampere

Ampere, A

SI Base Unit

Electric Current, I

SI Base Quantity

This unit of electric current (1 amp) is the flow capacity of the electric charge in one coulomb over a duration of one second. One coulomb is equivalent to the charge of 6.242×10¹⁸ electrons.

Formally, as defined in 2014:
“The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1m apart in vacuum, would produce between these conductors a force equal to 2 × 10⁻⁷ newton per metre of length.”

Proposed:
“The ampere, A, is the unit of electric current; its magnitude is set by fixing the numerical value of the elementary charge to be equal to exactly 1.602 17X × 10⁻¹⁹ when it is expressed in the unit A·s, which is equal to C.”

Discovered by
André-Marie Ampère, 1820

Candela

Candela, cd

SI Base Unit

Luminous Intensity, J

SI Base Quantity

This unit is based on a common candle emitting light with a luminous intensity of one candela. The amount of light illuminating a surface area is called the illuminance and is measured in lumens: 1 lumen = 1 candela x steradian. The energy of 1 candle (candela) passing through a spherical 360 degree surface area with a 1 metre radius, will give a sphere surface area of 4 pi r² = 12.57 m² = 12.57 lumens. With an apex angle of 360°: 1 candela = 12.57 lumen, 1 lumen = 0.08 candela. With a surface area of 12.57m²: 1 lumen = 0.08 lux, 1 lux = 12.57 lumen.
At a distance of 1m: 1 candela = 1 lux, 1 lux = 1 candela.

Formally, as defined in 2014:
"The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 × 10¹² Hz and that has a radiant intensity in that direction of 1/683 watt per steradian"

Proposed:
"The candela, cd, is the unit of luminous intensity in a given direction; its magnitude is set by fixing the numerical value of the luminous efficacy of monochromatic radiation of frequency 540 × 10¹² Hz to be equal to exactly 683 when it is expressed in the unit s³·m^-2·kg^-1·cd·sr, or cd·sr·W^-1, which is equal to lm·W^-1.”

Discovered by Jules Louis Gabriel Violle, 1881

Candela

Candela, cd

SI Base Unit

Luminous Intensity, J

SI Base Quantity

This unit is based on a common candle emitting light with a luminous intensity of one candela. The amount of light illuminating a surface area is called the illuminance and is measured in lumens: 1 lumen = 1 candela x steradian. The energy of 1 candle (candela) passing through a spherical 360 degree surface area with a 1 metre radius, will give a sphere surface area of 4 pi r² = 12.57 m² = 12.57 lumens. With an apex angle of 360°: 1 candela = 12.57 lumen, 1 lumen = 0.08 candela. With a surface area of 12.57m²: 1 lumen = 0.08 lux, 1 lux = 12.57 lumen.
At a distance of 1m: 1 candela = 1 lux, 1 lux = 1 candela.

Formally, as defined in 2014:
"The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 × 10¹² Hz and that has a radiant intensity in that direction of 1/683 watt per steradian"

Proposed:
"The candela, cd, is the unit of luminous intensity in a given direction; its magnitude is set by fixing the numerical value of the luminous efficacy of monochromatic radiation of frequency 540 × 10¹² Hz to be equal to exactly 683 when it is expressed in the unit s³·m^-2·kg^-1·cd·sr, or cd·sr·W^-1, which is equal to lm·W^-1.”

Discovered by
Jules Louis Gabriel Violle, 1881

Kelvin

Kelvin, K

SI Base Unit

Temperature, Θ

SI Base Quantity

The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all thermal motion ceases in the classical description of thermodynamics. The kelvin is defined as the fraction 1⁄273.16 of the thermodynamic temperature of the triple point of water (exactly 0.01 °C or 32.018 °F). The triple point of water is exactly 273.16 K.

Formally, as defined in 2014:
“The kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water.”

Proposed:
“The kelvin, K, is the unit of thermodynamic temperature; its magnitude is set by fixing the numerical value of the Boltzmann constant to be equal to exactly 1.380 65X × 10⁻²³ when it is expressed in the unit s⁻²·m²·kg·K⁻¹, which is equal to J·K⁻¹.”

Discovered by Lord William Kelvin, 1848

Kelvin

Kelvin, K

SI Base Unit

Temperature, Θ

SI Base Quantity

The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all thermal motion ceases in the classical description of thermodynamics. The kelvin is defined as the fraction 1⁄273.16 of the thermodynamic temperature of the triple point of water (exactly 0.01 °C or 32.018 °F). The triple point of water is exactly 273.16 K.

Formally, as defined in 2014:
“The kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water.”

Proposed:
“The kelvin, K, is the unit of thermodynamic temperature; its magnitude is set by fixing the numerical value of the Boltzmann constant to be equal to exactly 1.380 65X × 10⁻²³ when it is expressed in the unit s⁻²·m²·kg·K⁻¹, which is equal to J·K⁻¹.”

Discovered by
Lord William Kelvin, 1848

Kilogram

Kilogram, kg

SI Base Unit

Mass, M

SI Base Quantity

The gram, 1/1000th of a kilogram, was originally defined as the mass of one cubic centimetre of water at the melting point of water. The original prototype kilogram, manufactured in 1799, has a mass equal to the mass of 1.000'028 dm³ of water at its maximum density at approximately 4 °C. The kilogram is the only SI base unit with a prefix (kilo) as part of its name and directly defined by an artefact rather than a fundamental physical property. Three SI Base units (Cd, A, mol) and 17 SI Derived units (N, Pa, J, W, C, V, F, Ω, S, Wb, T, H, kat, Gy, Sv, lm, lx) are defined relative to the kilogram. Only 8 SI units do not require the kilogram in their definition: temperature (K, °C), time and frequency (s, Hz, Bq), length (m), and angle (rad, sr). The International Committee for Weights and Measures have undertaken to redefine the kilogram in terms of a fundamental constant of nature, as in the Planck constant.

Formally, as defined in 2014:
"The kilogram is the unit of mass; it is equal to the mass of the international prototype of the kilogram."

Proposed:
"The kilogram, kg, is the unit of mass; its magnitude is set by fixing the numerical value of the Planck constant to be equal to exactly 6.626 06X × 10⁻³⁴ when it is expressed in the unit s⁻¹·m²·kg, which is equal to J·s.”

Metre

Metre, m

SI Base Unit

Length, L

SI Base Quantity

Originally defined as one ten-millionth of the distance from the equator to the North Pole. In 1889, it was redefined in terms of a prototype metre bar then in 1960, the metre was redefined as equal to 1 650 763.73 wavelengths of the orange-red emission line in the electromagnetic spectrum of the krypton-86 atom in a vacuum. The metre is now defined as the path length travelled by light in a given time with practical laboratory length measurements, in metres, determined by counting the number of wavelengths of laser light and converting the selected unit of wavelength to metres. Three major factors limit this accuracy for length measurement: Uncertainty in vacuum wavelength of the source, refractive index of the medium and count resolution of the interferometer.

Formally, as defined in 2014:
"The metre is the length of the path travelled by light in vacuum during a time interval of 1/299,792,458 of a second."

Proposed:
"The metre, m, is the unit of length; its magnitude is set by fixing the numerical value of the speed of light in vacuum to be equal to exactly 299,792,458 when it is expressed in the unit m·s⁻¹.”

Mole

Mole, mol

SI Base Unit

Amount of Substance, N

SI Base Quantity

The mass per mole of a substance is called its molar mass and is measured in grams per mole, exactly equal to its mean molecular or atomic mass, that is measured in unified atomic mass units. The number of elementary entities in a sample of a substance is technically called its (chemical) amount, the unit for that physical quantity, the mole and can be determined by dividing the mass of the sample by the molar mass of the substance.

Formally, as defined in 2014:
"The mole is the amount of substance of a system that contains as many elementary entities as there are atoms in 0.012 kilogram of carbon-12. When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles."

Proposed:
"The mole, mol, is the unit of amount of substance of a specified elementary entity, which may be an atom, molecule, ion, electron, any other particle or a specified group of such particles; its magnitude is set by fixing the numerical value of the Avogadro constant to be equal to exactly 6.022 14X × 10²³ when it is expressed in the unit mol⁻¹.”

Second

Second, s

SI Base Unit

Time, T

SI Base Quantity

Time divisions began with the earliest civilizations with night and day, then recorded in 2000 BC day and night became twelve hours each. Then after 300 BC, the Babylonians subdivided the day using the sexagesimal system and divided each subsequent subdivision by sixty, then to at least six places after the sexagesimal point, a precision equivalent to 2 microseconds.

The first use of the second was in 1000 AD by a Persian scholar Al-Biruni and defined the division of time between new moons of certain specific weeks as a number of days, hours, minutes, seconds, thirds, and fourths after noon Sunday. The modern second is subdivided using decimals and the earliest clocks to display seconds appeared post 1560 AD on an unsigned clock depicting Orpheus in the Fremersdorf collection. In 1644 AD, Marin Mersenne, calculated that a pendulum with a length of 39.1 inches (0.994 m) would have a period at one standard gravity of precisely two seconds, one second for a swing forward and one second for the return swing, enabling a pendulum to tick in precise seconds.

In 1832, mathematician and physicist, Johann Carl Friedrich Gauss proposed using the second as the base unit of time in his millimetre-milligram-second system of units, defining the second as 1⁄86,400 of a mean solar day. In 1956, the second was redefined in terms of a year (the period of the Earth's revolution around the Sun) for a particular epoch, described in Newcomb's Tables of the Sun (1895), which provided a formula for estimating the motion of the Sun relative to the epoch 1900 based on astronomical observations made between 1750 and 1892.

In 1960, the second was defined as 1⁄31,556,925.974'7 of the tropical year for 1900 January 0 at 12-hour ephemeris time, abandoning any explicit relationship between the scientific second and the length of a day.

Formally, as defined in 2014:
"The second is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom."

Proposed:
"The second, s, is the unit of time; its magnitude is set by fixing the numerical value of the ground state hyperfine splitting frequency of the caesium-133 atom, at rest and at a temperature of 0 K, to be equal to exactly 9,192,631,770 when it is expressed in the unit s−1, which is equal to Hz."

Invented by Claudius Ptolemy, 150 AD

Second

Second, s

SI Base Unit

Time, T

SI Base Quantity

Time divisions began with the earliest civilizations with night and day, then recorded in 2000 BC day and night became twelve hours each. Then after 300 BC, the Babylonians subdivided the day using the sexagesimal system and divided each subsequent subdivision by sixty, then to at least six places after the sexagesimal point, a precision equivalent to 2 microseconds.

The first use of the second was in 1000 AD by a Persian scholar Al-Biruni and defined the division of time between new moons of certain specific weeks as a number of days, hours, minutes, seconds, thirds, and fourths after noon Sunday. The modern second is subdivided using decimals and the earliest clocks to display seconds appeared post 1560 AD on an unsigned clock depicting Orpheus in the Fremersdorf collection. In 1644 AD, Marin Mersenne, calculated that a pendulum with a length of 39.1 inches (0.994 m) would have a period at one standard gravity of precisely two seconds, one second for a swing forward and one second for the return swing, enabling a pendulum to tick in precise seconds.

In 1832, mathematician and physicist, Johann Carl Friedrich Gauss proposed using the second as the base unit of time in his millimetre-milligram-second system of units, defining the second as 1⁄86,400 of a mean solar day. In 1956, the second was redefined in terms of a year (the period of the Earth's revolution around the Sun) for a particular epoch, described in Newcomb's Tables of the Sun (1895), which provided a formula for estimating the motion of the Sun relative to the epoch 1900 based on astronomical observations made between 1750 and 1892.

In 1960, the second was defined as 1⁄31,556,925.974'7 of the tropical year for 1900 January 0 at 12-hour ephemeris time, abandoning any explicit relationship between the scientific second and the length of a day.

Formally, as defined in 2014:
"The second is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom."

Proposed:
"The second, s, is the unit of time; its magnitude is set by fixing the numerical value of the ground state hyperfine splitting frequency of the caesium-133 atom, at rest and at a temperature of 0 K, to be equal to exactly 9,192,631,770 when it is expressed in the unit s−1, which is equal to Hz."

Invented by
Claudius Ptolemy, 150 AD

DERIVED UNITS

BASE · DERIVED
DECIMAL · BINARY · CONVERSION

DERIVED UNITS

Becquerel

Becquerel, Bq

SI Derived Unit

Activity re Radionuclide

SI Derived Quantity

s^-1

SI Base Expression

This unit is defined as the activity of a quantity of radioactive material in which one nucleus decays per second and is equivalent to an inverse second, s⁻¹.

Named after Antoine Henri Becquerel

Becquerel

Becquerel, Bq

SI Derived Unit

Activity re Radionuclide

SI Derived Quantity

s^-1

SI Base Expression

This unit is defined as the activity of a quantity of radioactive material in which one nucleus decays per second and is equivalent to an inverse second, s⁻¹.

Named after
Antoine Henri Becquerel

Coulomb

Coulomb, C

SI Derived Unit

Electric Charge, Amount of Electricity

SI Derived Quantity

A·s

SI Base Expression

This base unit of electrical charge is equal to 6.25 X 10¹⁸ electrons. Named for Charles Coulomb, the French physicist who pioneered research into magnetism and electricity, whom also formulated Coulomb's law which states that the force of attraction or repulsion between two charged bodies is equal to the product of the two charges and is inversely proportional to the square of the distance between them.

Named after Charles Augustin de Coulomb

Coulomb

Coulomb, C

SI Derived Unit

Electric Charge, Amount of Electricity

SI Derived Quantity

A·s

SI Base Expression

This base unit of electrical charge is equal to 6.25 X 10¹⁸ electrons. Named for Charles Coulomb, the French physicist who pioneered research into magnetism and electricity, whom also formulated Coulomb's law which states that the force of attraction or repulsion between two charged bodies is equal to the product of the two charges and is inversely proportional to the square of the distance between them.

Named after
Charles Augustin de Coulomb

Degrees Celsius

Degrees Celsius, °C

SI Derived Unit

Celsius Temperature

SI Derived Quantity

K

SI Base Expression

Celsius, historically known as centigrade, is a scale and unit of measurement for temperature. From 1744 to 1954, 0 °C was defined as the freezing point of water and 100 °C was defined as the boiling point of water, both at a pressure of one standard atmosphere with mercury being the working material. Absolute zero, the lowest temperature possible, is defined as being precisely 0 K and −273.15 °C.

Named after Anders Celsius

Degrees Celsius

Degrees Celsius, °C

SI Derived Unit

Celsius Temperature

SI Derived Quantity

K

SI Base Expression

Celsius, historically known as centigrade, is a scale and unit of measurement for temperature. From 1744 to 1954, 0 °C was defined as the freezing point of water and 100 °C was defined as the boiling point of water, both at a pressure of one standard atmosphere with mercury being the working material. Absolute zero, the lowest temperature possible, is defined as being precisely 0 K and −273.15 °C.

Named after
Anders Celsius

Farad

Farad, F

SI Derived Unit

Capacitance

SI Derived Quantity

kg⁻¹·m⁻²·s⁴·A²

SI Base Expression

One farad of capacitance will store one coulomb of charge when the charging force is one volt. Since the farad is a very large unit, capacitance will more commonly expressed as microfarad (uF) or picofarad (pF) values.

Named after Michael Faraday

Farad

Farad, F

SI Derived Unit

Capacitance

SI Derived Quantity

kg⁻¹·m⁻²·s⁴·A²

SI Base Expression

One farad of capacitance will store one coulomb of charge when the charging force is one volt. Since the farad is a very large unit, capacitance will more commonly expressed as microfarad (uF) or picofarad (pF) values.

Named after
Michael Faraday

Gray

Gray, Gy

SI Derived Unit

Absorbed Dose, Specific Energy (Imparted), Kerma

SI Derived Quantity

m²·s⁻²

SI Base Expression

This unit is defined as the absorption of one joule of radiation energy per one kilogram of matter. It is used as a measure of absorbed dose, specific energy (imparted), and kerma (an acronym for “kinetic energy released per unit mass”). It is a physical quantity, and does not take into account any biological context. Unlike the pre-1971 non-SI roentgen unit of radiation exposure, the Gray when used for absorbed dose is defined independently of any target material. When measuring kerma the reference target material must be defined explicitly, usually as dry air at standard temperature and pressure.

Named after Louis Harold Gray

Gray

Gray, Gy

SI Derived Unit

Absorbed Dose, Specific Energy (Imparted), Kerma

SI Derived Quantity

m²·s⁻²

SI Base Expression

This unit is defined as the absorption of one joule of radiation energy per one kilogram of matter. It is used as a measure of absorbed dose, specific energy (imparted), and kerma (an acronym for “kinetic energy released per unit mass”). It is a physical quantity, and does not take into account any biological context. Unlike the pre-1971 non-SI roentgen unit of radiation exposure, the Gray when used for absorbed dose is defined independently of any target material. When measuring kerma the reference target material must be defined explicitly, usually as dry air at standard temperature and pressure.

Named after
Louis Harold Gray

Henry

Henry, H

SI Derived Unit

Inductance

SI Derived Quantity

kg · m² · s⁻² · A⁻²

SI Base Expression

This is the unit of inductance in which an induced electromotive force of one volt is produced when the current is varied at the rate of one ampere per second.

Named after Joseph Henry

Henry

Henry, H

SI Derived Unit

Inductance

SI Derived Quantity

kg · m² · s⁻² · A⁻²

SI Base Expression

This is the unit of inductance in which an induced electromotive force of one volt is produced when the current is varied at the rate of one ampere per second.

Named after
Joseph Henry

Hertz

Hertz, Hz

SI Derived Unit

Frequency

SI Derived Quantity

s^-1

SI Base Expression

This unit of frequency is equal to cycles per second. In defining the second, "the standard to be employed is the transition between the hyperfine levels F = 4, M = 0 and F = 3, M = 0 of the ground state 2S_1/2 of the caesium 133 atom, unperturbed by external fields, and that the frequency of this transition is assigned the value 9,192,631,770 hertz", effectively defining the hertz and the second simultaneously.

Named after Heinrich Hertz

Hertz

Hertz, Hz

SI Derived Unit

Frequency

SI Derived Quantity

s^-1

SI Base Expression

This unit of frequency is equal to cycles per second. In defining the second, "the standard to be employed is the transition between the hyperfine levels F = 4, M = 0 and F = 3, M = 0 of the ground state 2S_1/2 of the caesium 133 atom, unperturbed by external fields, and that the frequency of this transition is assigned the value 9,192,631,770 hertz", effectively defining the hertz and the second simultaneously.

Named after
Heinrich Hertz

Joule

Joule, J

SI Derived Unit

Energy, Work, Amount of Heat

SI Derived Quantity

kg·m²·s⁻²

SI Base Expression

This is the basic unit of electrical, mechanical, and thermal energy. As a unit of electrical energy it is equal to the energy carried by 1 coulomb of charge being propelled by an electromotive force of 1 volt.

Named after Joseph Henry

Joule

Joule, J

SI Derived Unit

Energy, Work, Amount of Heat

SI Derived Quantity

kg·m²·s⁻²

SI Base Expression

This is the basic unit of electrical, mechanical, and thermal energy. As a unit of electrical energy it is equal to the energy carried by 1 coulomb of charge being propelled by an electromotive force of 1 volt.

Named after
Joseph Henry

Katal

Katal, kat

SI Derived Unit

Catalytic Activity

SI Derived Quantity

mol · s^-1

SI Base Expression

This is a unit for quantifying the catalytic activity of enzymes (measuring the enzymatic activity level in enzyme catalysis) and other catalysts. The katal is not used to express the rate of a reaction; that is expressed in units of concentration per second (or moles per litre per second). It is used to express catalytic activity which is a property of the catalyst.

Lumen

Lumen, lm

SI Derived Unit

Luminous Flux

SI Derived Quantity

cd · sr

SI Base Expression

This is a measure of the total "amount" of visible light emitted by a source. Luminous flux differs from power (Radiant Flux) in that luminous flux measurements reflect the varying sensitivity of the human eye to different wavelengths of light. Radiant flux measurements indicate the total power of all electromagnetic waves emitted, independent of the eye's ability to perceive it. Lumens are related to lux in that one lux is one lumen per square meter.

Lux

Lux, lx

SI Derived Unit

Illuminance

SI Derived Quantity

cd · sr · m⁻²

SI Base Expression

This is a measure of how much luminous flux (lumens) is spread over a given area. One lux is equal to one lumen per square metre.

Newton

Newton, N

SI Derived Unit

Force

SI Derived Quantity

kg · m · s⁻²

SI Base Expression

Force (F) is any interaction when unopposed, will change the motion of an object. A force can cause an object with mass to change its velocity, which includes to begin moving from a state of rest, as in to accelerate. Weight (W) of an object is the force on the object due to gravity. Weight is the product of the mass (m) of the object and the magnitude of the local gravitational acceleration (g), thus: W = mg.

Named after Sir Isaac Newton

Newton

Newton, N

SI Derived Unit

Force

SI Derived Quantity

kg · m · s⁻²

SI Base Expression

Force (F) is any interaction when unopposed, will change the motion of an object. A force can cause an object with mass to change its velocity, which includes to begin moving from a state of rest, as in to accelerate. Weight (W) of an object is the force on the object due to gravity. Weight is the product of the mass (m) of the object and the magnitude of the local gravitational acceleration (g), thus: W = mg.

Named after
Sir Isaac Newton

Ohm

Ohm, Ω

SI Derived Unit

Electric Resistance

SI Derived Quantity

kg · m² · s⁻³ · A⁻²

SI Base Expression

The ohm is defined as an electrical resistance between two points of a conductor when a constant potential difference of 1 volt, applied to these points, produces in the conductor a current of 1 ampere, the conductor not being the seat of any electromotive force. In alternating current circuits, electrical impedance is also measured in ohms (Ω).

Named after Georg Simon Ohm

Ohm

Ohm, Ω

SI Derived Unit

Electric Resistance

SI Derived Quantity

kg · m² · s⁻³ · A⁻²

SI Base Expression

The ohm is defined as an electrical resistance between two points of a conductor when a constant potential difference of 1 volt, applied to these points, produces in the conductor a current of 1 ampere, the conductor not being the seat of any electromotive force. In alternating current circuits, electrical impedance is also measured in ohms (Ω).

Named after
Georg Simon Ohm

Pascal

Pascal, Pa

SI Derived Unit

Pressure, Stress

SI Derived Quantity

kg · m^-1 · s⁻²

SI Base Expression

The pascal (Pa), is one newton per square metre. Pressure (P) is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure. Multiple units of the pascal are the hectopascal (1 hPa ≡ 100 Pa) which is equal to 1 mbar, the kilopascal (1 kPa ≡ 1,000 Pa), the megapascal (1 MPa ≡ 1,000,000 Pa), and the gigapascal (1 GPa ≡ 1,000,000,000 Pa). The unit of measurement called the standard atmosphere (atm) is defined as 101.325 kPa and approximates to the average pressure at sea-level at 45° N.

Named after Blaise Pascal

Pascal

Pascal, Pa

SI Derived Unit

Pressure, Stress

SI Derived Quantity

kg · m^-1 · s⁻²

SI Base Expression

The pascal (Pa), is one newton per square metre. Pressure (P) is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure. Multiple units of the pascal are the hectopascal (1 hPa ≡ 100 Pa) which is equal to 1 mbar, the kilopascal (1 kPa ≡ 1,000 Pa), the megapascal (1 MPa ≡ 1,000,000 Pa), and the gigapascal (1 GPa ≡ 1,000,000,000 Pa). The unit of measurement called the standard atmosphere (atm) is defined as 101.325 kPa and approximates to the average pressure at sea-level at 45° N.

Named after
Blaise Pascal

Radian

Radian, rad

SI Derived Unit

Plane Angle

SI Derived Quantity

m/m

SI Base Expression

An angle's measurement in radians is numerically equal to the length of a corresponding arc of a unit circle; one radian is just under 57.3 degrees (when the arc length is equal to the radius). One radian is equal to 180/π degrees. To convert from radians to degrees, multiply by 180/π.

Named after Roger Cotes

Radian

Radian, rad

SI Derived Unit

Plane Angle

SI Derived Quantity

m/m

SI Base Expression

An angle's measurement in radians is numerically equal to the length of a corresponding arc of a unit circle; one radian is just under 57.3 degrees (when the arc length is equal to the radius). One radian is equal to 180/π degrees. To convert from radians to degrees, multiply by 180/π.

Named after
Roger Cotes

Siemen

Siemen, S

SI Derived Unit

Electric Conductance

SI Derived Quantity

kg⁻¹ · m⁻² · s³ · A²

SI Base Expression

This is the unit of electric conductance, electric susceptance and electric admittance which are the reciprocals of resistance, reactance, and impedance. One siemens is equal to the reciprocal of one ohm, and is also referred to as the mho.

Named after Ernst Werner von Siemens

Siemen

Siemen, S

SI Derived Unit

Electric Conductance

SI Derived Quantity

kg⁻¹ · m⁻² · s³ · A²

SI Base Expression

This is the unit of electric conductance, electric susceptance and electric admittance which are the reciprocals of resistance, reactance, and impedance. One siemens is equal to the reciprocal of one ohm, and is also referred to as the mho.

Named after
Ernst Werner von Siemens

Sievert

Sievert, Sv

SI Derived Unit

Ambient, Directional, Dose and Personal Dose Equivalent

SI Derived Quantity

m² · s⁻²

SI Base Expression

This is a measure of the health effect of low levels of ionizing radiation on the human body. Quantities that are measured in sieverts are intended to represent the stochastic health risk, which for radiation dose assessment is defined as the probability of cancer induction and genetic. The sievert is used for radiation dose quantities such as equivalent dose, effective dose, and committed dose. It is used both to represent the risk of the effect of external radiation from sources outside the body, and the effect of internal irradiation due to inhaled or ingested radioactive substances. One sievert carries with it a 5.5% chance of eventually developing cancer.

Named after Rolf Maximilian Sievert

Sievert

Sievert, Sv

SI Derived Unit

Ambient, Directional, Dose and Personal Dose Equivalent

SI Derived Quantity

m² · s⁻²

SI Base Expression

This is a measure of the health effect of low levels of ionizing radiation on the human body. Quantities that are measured in sieverts are intended to represent the stochastic health risk, which for radiation dose assessment is defined as the probability of cancer induction and genetic. The sievert is used for radiation dose quantities such as equivalent dose, effective dose, and committed dose. It is used both to represent the risk of the effect of external radiation from sources outside the body, and the effect of internal irradiation due to inhaled or ingested radioactive substances. One sievert carries with it a 5.5% chance of eventually developing cancer.

Named after
Rolf Maximilian Sievert

Steradian

Steradian, sr

SI Derived Unit

Solid Angle

SI Derived Quantity

m²/m²

SI Base Expression

Also known as the square radian, it is used in three-dimensional geometry and is analogous to the radian which quantifies planar angles. This solid angle is the ratio between the area subtended and the square of its distance from the vertex: both the numerator and denominator of this ratio have dimension length squared.

Tesla

Tesla, T

SI Derived Unit

Magnetic Flux Density

SI Derived Quantity

kg · s⁻² · A⁻¹

SI Base Expression

This is the measurement for the strength of the magnetic field. One tesla is equal to one weber per square metre. A particle, that is carrying the charge of 1 coulomb, passing through a magnetic field of 1 tesla, perpendicular and at a speed of 1 metre per second, experiences a force of magnitude 1 newton.

Named after Nicola Tesla

Tesla

Tesla, T

SI Derived Unit

Magnetic Flux Density

SI Derived Quantity

kg · s⁻² · A⁻¹

SI Base Expression

This is the measurement for the strength of the magnetic field. One tesla is equal to one weber per square metre. A particle, that is carrying the charge of 1 coulomb, passing through a magnetic field of 1 tesla, perpendicular and at a speed of 1 metre per second, experiences a force of magnitude 1 newton.

Named after
Nicola Tesla

Volt

Volt, V

SI Derived Unit

Electric Potential Difference, Electromotive Force

SI Derived Quantity

kg · m² · s⁻³ · A⁻¹

SI Base Expression

This is the measurement for the strength of the magnetic field. One tesla is equal to one weber per square metre. A particle, that is carrying the charge of 1 coulomb, passing through a magnetic field of 1 tesla, perpendicular and at a speed of 1 metre per second, experiences a force of magnitude 1 newton.

Named after Alessandro Giuseppe Antonio Anastasio Volta

Volt

Volt, V

SI Derived Unit

Electric Potential Difference, Electromotive Force

SI Derived Quantity

kg · m² · s⁻³ · A⁻¹

SI Base Expression

This is the measurement for the strength of the magnetic field. One tesla is equal to one weber per square metre. A particle, that is carrying the charge of 1 coulomb, passing through a magnetic field of 1 tesla, perpendicular and at a speed of 1 metre per second, experiences a force of magnitude 1 newton.

Named after
Alessandro Giuseppe Antonio Anastasio Volta

Watt

Watt, W

SI Derived Unit

Power, Radiant Flux

SI Derived Quantity

kg · m² · s⁻³

SI Base Expression

This unit is defined as joule per second and is used to express the rate of energy conversion or transfer with respect to time.

Named after James Watt

Watt

Watt, W

SI Derived Unit

Power, Radiant Flux

SI Derived Quantity

kg · m² · s⁻³

SI Base Expression

This unit is defined as joule per second and is used to express the rate of energy conversion or transfer with respect to time.

Named after
James Watt

Webber

Webber, Wb

SI Derived Unit

Magnetic Flux

SI Derived Quantity

kg · m² · s⁻² · A⁻¹

SI Base Expression

This unit is defined as joule per second and is used to express the rate of energy conversion or transfer with respect to time.

DECIMAL UNITS

BASE · DERIVED
DECIMAL · BINARY · CONVERSION

DECIMAL UNITS

SI Prefixes (Decimal)

N S K P D

Yotta Y Septillion 10²⁴ 1,000,000,000,000,000,000,000,000

Zetta Z Sextillion 10²¹ 1,000,000,000,000,000,000,000

Exa E Quintillion 10¹⁸ 1,000,000,000,000,000,000

Peta P Quadrillion 10¹⁵ 1,000,000,000,000,000

Tera T Trillion 10¹² 1,000,000,000,000

Giga G Billion 10⁹ 1,000,000,000

Mega M Million 10⁶ 1,000,000

Kilo k Thousand 10³ 1,000

Hecto h Hundred 10² 100

Deca da Ten 10¹ 10

Unit 1 One 10⁰ 1

Deci d Tenth 10^-1 0.1

Centi c Hundredth 10^-2 0.01

Milli m Thousandth 10^-3 0.001

Micro μ Millionth 10^-6 0.000'001

Nano n Billionth 10^-9 0.000'000'001

Pico p Trillionth 10^-12 0.000'000'000'001

Femto f Quadrillionth 10^-15 0.000'000'000'000'001

Atto a Quintillionth 10^-18 0.000'000'000'000'000'001

Zepto z Sextillionth 10^-21 0.000'000'000'000'000'000'001

Yocto y Septillionth 10^-24 0.000'000'000'000'000'000'000'001

SI Prefixes (Decimal)

N S K P

Yotta Y Septillion 10²⁴

Zetta Z Sextillion 10²¹

Exa E Quintillion 10¹⁸

Peta P Quadrillion 10¹⁵

Tera T Trillion 10¹²

Giga G Billion 10⁹

Mega M Million 10⁶

Kilo k Thousand 10³

Hecto h Hundred 10²

Deca da Ten 10¹

Unit 1 One 10⁰

Deci d Tenth 10^-1

Centi c Hundredth 10^-2

Milli m Thousandth 10^-3

Micro μ Millionth 10^-6

Nano n Billionth 10^-9

Pico p Trillionth 10^-12

Femto f Quadrillionth 10^-15

Atto a Quintillionth 10^-18

Zepto z Sextillionth 10^-21

Yocto y Septillionth 10^-24

BINARY UNITS

BASE · DERIVED
DECIMAL · BINARY · CONVERSION

BINARY UNITS

SI Prefixes (Binary)

N S K P D

Yobi Yi Yottabinary (2¹⁰)⁸ 1,208,925,819,614,629,174,706,176

Zebi Zi Zettabinary (2¹⁰)⁷ 1,180,591,620,717,411,303,424

Exbi Ei Exabinary (2¹⁰)⁶ 1,152,921,504,606,850,000

Pebi Pi Petabinary (2¹⁰)⁵ 1,125,899,906,842,620

Tebi Ti Terabinary (2¹⁰)⁴ 1,099,511,627,776

Gibi Gi Gigabinary (2¹⁰)³ 1,073,741,824

Mebi Mi Megabinary (2¹⁰)² 1,048,576

Kibi Ki Kilobinary (2¹⁰)¹ 1,024

Unit 1 One (10⁰) 1

SI Prefixes (Binary)

N S K P

Yobi Yi Yottabinary (2¹⁰)⁸

Zebi Zi Zettabinary (2¹⁰)⁷

Exbi Ei Exabinary (2¹⁰)⁶

Pebi Pi Petabinary (2¹⁰)⁵

Tebi Ti Terabinary (2¹⁰)⁴

Gibi Gi Gigabinary (2¹⁰)³

Mebi Mi Megabinary (2¹⁰)²

Kibi Ki Kilobinary (2¹⁰)¹

Unit 1 One (10⁰)

CONVERSION UNITS

BASE · DERIVED
DECIMAL · BINARY · CONVERSION

CONVERSION UNITS

Conversion of SI to CGS Units

SI Units
(French: Système International d'Unités)
Gaussian Units
(CGS: Centimetre-Gram-Second)

Electric Charge, q
1 C (SI) = (10⁻¹ c) Fr (CGS)

Electric Current, I
1 A (SI) = (10⁻¹ c) Fr/s (CGS)

Electric Potential, φ · V
1 V (SI) = (10⁸ csup>−1) statV (CGS)

Electric Field, E
1 V/m (SI) = (10⁶ c⁻¹) statV/cm (CGS)

Magnetic Induction, B
1 T (SI) = (10⁴) Gs (CGS)

Magnetic Field Strength, H
1 A/m (SI) = (4π 10⁻³) Oe (CGS)

Magnetic Dipole Moment, μ
1 A·m² (SI) = (10³) erg/Gs (CGS)

Magnetic Flux, Φ_m
1 Wb (SI) = (10⁸) Gs·cm² (CGS)

Resistance, R
1 Ω (SI) = (10⁹ c⁻²) s/cm (CGS)

Resistivity, ρ
1 Ω·m (SI) = (10¹¹ c⁻²) s (CGS)

Capacitance, C
1 F (SI) = (10⁻⁹ c²) cm (CGS)

Inductance, L
1 H (SI) = (10⁹ c⁻²) s²/cm (CGS)

Conversion of SI to CGS Units

Conversion of SI to CGS Units

Electric Charge, q
1 C (SI) = (10⁻¹ c) Fr (CGS)

Electric Current, I
1 A (SI) = (10⁻¹ c) Fr/s (CGS)

Electric Potential, φ · V
1 V (SI) = (10⁸ csup>−1) statV (CGS)

Electric Field, E
1 V/m (SI) = (10⁶ c⁻¹) statV/cm (CGS)

Magnetic Induction, B
1 T (SI) = (10⁴) Gs (CGS)

Magnetic Field Strength, H
1 A/m (SI) = (4π 10⁻³) Oe (CGS)

Magnetic Dipole Moment, μ
1 A·m² (SI) = (10³) erg/Gs (CGS)

Magnetic Flux, Φ_m
1 Wb (SI) = (10⁸) Gs·cm² (CGS)

Resistance, R
1 Ω (SI) = (10⁹ c⁻²) s/cm (CGS)

Resistivity, ρ
1 Ω·m (SI) = (10¹¹ c⁻²) s (CGS)

Capacitance, C
1 F (SI) = (10⁻⁹ c²) cm (CGS)

Inductance, L
1 H (SI) = (10⁹ c⁻²) s²/cm (CGS)

Conversion of SI to CGS Units

Electric Charge, q
1 C (SI) = (10⁻¹ c) Fr (CGS)

Electric Current, I
1 A (SI) = (10⁻¹ c) Fr/s (CGS)

Electric Potential, φ · V
1 V (SI) = (10⁸ csup>−1) statV (CGS)

Electric Field, E
1 V/m (SI) = (10⁶ c⁻¹) statV/cm (CGS)

Magnetic Induction, B
1 T (SI) = (10⁴) Gs (CGS)

Magnetic Field Strength, H
1 A/m (SI) = (4π 10⁻³) Oe (CGS)

Magnetic Dipole Moment, μ
1 A·m² (SI) = (10³) erg/Gs (CGS)

Magnetic Flux, Φ_m
1 Wb (SI) = (10⁸) Gs·cm² (CGS)

Resistance, R
1 Ω (SI) = (10⁹ c⁻²) s/cm (CGS)

Resistivity, ρ
1 Ω·m (SI) = (10¹¹ c⁻²) s (CGS)

Capacitance, C
1 F (SI) = (10⁻⁹ c²) cm (CGS)

Inductance, L
1 H (SI) = (10⁹ c⁻²) s²/cm (CGS)

Conversion of
SI to CGS Units

Electric Charge, q
1 C (SI) = (10⁻¹ c) Fr (CGS)

Electric Current, I
1 A (SI) = (10⁻¹ c) Fr/s (CGS)

Electric Potential, φ · V
1 V (SI) = (10⁸ csup>−1) statV (CGS)

Electric Field, E
1 V/m (SI) = (10⁶ c⁻¹) statV/cm (CGS)

Magnetic Induction, B
1 T (SI) = (10⁴) Gs (CGS)

Magnetic Field Strength, H
1 A/m (SI) = (4π 10⁻³) Oe (CGS)

Magnetic Dipole Moment, μ
1 A·m² (SI) = (10³) erg/Gs (CGS)

Magnetic Flux, Φ_m
1 Wb (SI) = (10⁸) Gs·cm² (CGS)

Resistance, R
1 Ω (SI) = (10⁹ c⁻²) s/cm (CGS)

Resistivity, ρ
1 Ω·m (SI) = (10¹¹ c⁻²) s (CGS)

Capacitance, C
1 F (SI) = (10⁻⁹ c²) cm (CGS)

Inductance, L
1 H (SI) = (10⁹ c⁻²) s²/cm (CGS)

	BASE UNITS
	BASE · DERIVED DECIMAL · BINARY · CONVERSION

	DERIVED UNITS
	BASE · DERIVED DECIMAL · BINARY · CONVERSION

	Becquerel, Bq SI Derived Unit
	Activity re Radionuclide SI Derived Quantity
	s^-1 SI Base Expression
	This unit is defined as the activity of a quantity of radioactive material in which one nucleus decays per second and is equivalent to an inverse second, s⁻¹. Named after Antoine Henri Becquerel

	Coulomb, C SI Derived Unit
	Electric Charge, Amount of Electricity SI Derived Quantity
	A·s SI Base Expression
	This base unit of electrical charge is equal to 6.25 X 10¹⁸ electrons. Named for Charles Coulomb, the French physicist who pioneered research into magnetism and electricity, whom also formulated Coulomb's law which states that the force of attraction or repulsion between two charged bodies is equal to the product of the two charges and is inversely proportional to the square of the distance between them. Named after Charles Augustin de Coulomb

	Degrees Celsius, °C SI Derived Unit
	Celsius Temperature SI Derived Quantity
	K SI Base Expression
	Celsius, historically known as centigrade, is a scale and unit of measurement for temperature. From 1744 to 1954, 0 °C was defined as the freezing point of water and 100 °C was defined as the boiling point of water, both at a pressure of one standard atmosphere with mercury being the working material. Absolute zero, the lowest temperature possible, is defined as being precisely 0 K and −273.15 °C. Named after Anders Celsius

	Farad, F SI Derived Unit
	Capacitance SI Derived Quantity
	kg⁻¹·m⁻²·s⁴·A² SI Base Expression
	One farad of capacitance will store one coulomb of charge when the charging force is one volt. Since the farad is a very large unit, capacitance will more commonly expressed as microfarad (uF) or picofarad (pF) values. Named after Michael Faraday

	Gray, Gy SI Derived Unit
	Absorbed Dose, Specific Energy (Imparted), Kerma SI Derived Quantity
	m²·s⁻² SI Base Expression
	This unit is defined as the absorption of one joule of radiation energy per one kilogram of matter. It is used as a measure of absorbed dose, specific energy (imparted), and kerma (an acronym for “kinetic energy released per unit mass”). It is a physical quantity, and does not take into account any biological context. Unlike the pre-1971 non-SI roentgen unit of radiation exposure, the Gray when used for absorbed dose is defined independently of any target material. When measuring kerma the reference target material must be defined explicitly, usually as dry air at standard temperature and pressure. Named after Louis Harold Gray

	Henry, H SI Derived Unit
	Inductance SI Derived Quantity
	kg · m² · s⁻² · A⁻² SI Base Expression
	This is the unit of inductance in which an induced electromotive force of one volt is produced when the current is varied at the rate of one ampere per second. Named after Joseph Henry

	Hertz, Hz SI Derived Unit
	Frequency SI Derived Quantity
	s^-1 SI Base Expression
	This unit of frequency is equal to cycles per second. In defining the second, "the standard to be employed is the transition between the hyperfine levels F = 4, M = 0 and F = 3, M = 0 of the ground state 2S_1/2 of the caesium 133 atom, unperturbed by external fields, and that the frequency of this transition is assigned the value 9,192,631,770 hertz", effectively defining the hertz and the second simultaneously. Named after Heinrich Hertz

	Joule, J SI Derived Unit
	Energy, Work, Amount of Heat SI Derived Quantity
	kg·m²·s⁻² SI Base Expression
	This is the basic unit of electrical, mechanical, and thermal energy. As a unit of electrical energy it is equal to the energy carried by 1 coulomb of charge being propelled by an electromotive force of 1 volt. Named after Joseph Henry

	Katal, kat SI Derived Unit
	Catalytic Activity SI Derived Quantity
	mol · s^-1 SI Base Expression
	This is a unit for quantifying the catalytic activity of enzymes (measuring the enzymatic activity level in enzyme catalysis) and other catalysts. The katal is not used to express the rate of a reaction; that is expressed in units of concentration per second (or moles per litre per second). It is used to express catalytic activity which is a property of the catalyst.

	Lumen, lm SI Derived Unit
	Luminous Flux SI Derived Quantity
	cd · sr SI Base Expression
	This is a measure of the total "amount" of visible light emitted by a source. Luminous flux differs from power (Radiant Flux) in that luminous flux measurements reflect the varying sensitivity of the human eye to different wavelengths of light. Radiant flux measurements indicate the total power of all electromagnetic waves emitted, independent of the eye's ability to perceive it. Lumens are related to lux in that one lux is one lumen per square meter.

	Lux, lx SI Derived Unit
	Illuminance SI Derived Quantity
	cd · sr · m⁻² SI Base Expression
	This is a measure of how much luminous flux (lumens) is spread over a given area. One lux is equal to one lumen per square metre.

	Newton, N SI Derived Unit
	Force SI Derived Quantity
	kg · m · s⁻² SI Base Expression
	Force (F) is any interaction when unopposed, will change the motion of an object. A force can cause an object with mass to change its velocity, which includes to begin moving from a state of rest, as in to accelerate. Weight (W) of an object is the force on the object due to gravity. Weight is the product of the mass (m) of the object and the magnitude of the local gravitational acceleration (g), thus: W = mg. Named after Sir Isaac Newton

	Ohm, Ω SI Derived Unit
	Electric Resistance SI Derived Quantity
	kg · m² · s⁻³ · A⁻² SI Base Expression
	The ohm is defined as an electrical resistance between two points of a conductor when a constant potential difference of 1 volt, applied to these points, produces in the conductor a current of 1 ampere, the conductor not being the seat of any electromotive force. In alternating current circuits, electrical impedance is also measured in ohms (Ω). Named after Georg Simon Ohm

	Pascal, Pa SI Derived Unit
	Pressure, Stress SI Derived Quantity
	kg · m^-1 · s⁻² SI Base Expression
	The pascal (Pa), is one newton per square metre. Pressure (P) is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure. Multiple units of the pascal are the hectopascal (1 hPa ≡ 100 Pa) which is equal to 1 mbar, the kilopascal (1 kPa ≡ 1,000 Pa), the megapascal (1 MPa ≡ 1,000,000 Pa), and the gigapascal (1 GPa ≡ 1,000,000,000 Pa). The unit of measurement called the standard atmosphere (atm) is defined as 101.325 kPa and approximates to the average pressure at sea-level at 45° N. Named after Blaise Pascal

	Radian, rad SI Derived Unit
	Plane Angle SI Derived Quantity
	m/m SI Base Expression
	An angle's measurement in radians is numerically equal to the length of a corresponding arc of a unit circle; one radian is just under 57.3 degrees (when the arc length is equal to the radius). One radian is equal to 180/π degrees. To convert from radians to degrees, multiply by 180/π. Named after Roger Cotes

	Siemen, S SI Derived Unit
	Electric Conductance SI Derived Quantity
	kg⁻¹ · m⁻² · s³ · A² SI Base Expression
	This is the unit of electric conductance, electric susceptance and electric admittance which are the reciprocals of resistance, reactance, and impedance. One siemens is equal to the reciprocal of one ohm, and is also referred to as the mho. Named after Ernst Werner von Siemens

	Sievert, Sv SI Derived Unit
	Ambient, Directional, Dose and Personal Dose Equivalent SI Derived Quantity
	m² · s⁻² SI Base Expression
	This is a measure of the health effect of low levels of ionizing radiation on the human body. Quantities that are measured in sieverts are intended to represent the stochastic health risk, which for radiation dose assessment is defined as the probability of cancer induction and genetic. The sievert is used for radiation dose quantities such as equivalent dose, effective dose, and committed dose. It is used both to represent the risk of the effect of external radiation from sources outside the body, and the effect of internal irradiation due to inhaled or ingested radioactive substances. One sievert carries with it a 5.5% chance of eventually developing cancer. Named after Rolf Maximilian Sievert

	Steradian, sr SI Derived Unit
	Solid Angle SI Derived Quantity
	m²/m² SI Base Expression
	Also known as the square radian, it is used in three-dimensional geometry and is analogous to the radian which quantifies planar angles. This solid angle is the ratio between the area subtended and the square of its distance from the vertex: both the numerator and denominator of this ratio have dimension length squared.

BASE UNITS BASE · DERIVED DECIMAL · BINARY · CONVERSION

BASE UNITS BASE · DERIVED DECIMAL · BINARY · CONVERSION

BASE UNITS BASE · DERIVED DECIMAL · BINARY · CONVERSION

BASE UNITS BASE · DERIVED DECIMAL · BINARY · CONVERSION

BASE UNITS

SI Base Unit

SI Base Quantity

Discovered by André-Marie Ampère, 1820

SI Base Unit

SI Base Quantity

Discovered by André-Marie Ampère, 1820

SI Base Unit

SI Base Quantity

Discovered by André-Marie Ampère, 1820

SI Base Unit

SI Base Quantity

Discovered by André-Marie Ampère, 1820

SI Base Unit

SI Base Quantity

Discovered by André-Marie Ampère, 1820

SI Base Unit

SI Base Quantity

Discovered by Jules Louis Gabriel Violle, 1881

SI Base Unit

SI Base Quantity

Discovered by Jules Louis Gabriel Violle, 1881

SI Base Unit

SI Base Quantity

Discovered by Jules Louis Gabriel Violle, 1881

SI Base Unit

SI Base Quantity

Discovered by Jules Louis Gabriel Violle, 1881

SI Base Unit

SI Base Quantity

Discovered by Jules Louis Gabriel Violle, 1881

SI Base Unit

SI Base Quantity

Discovered by Lord William Kelvin, 1848

SI Base Unit

SI Base Quantity

Discovered by Lord William Kelvin, 1848

SI Base Unit

SI Base Quantity

Discovered by Lord William Kelvin, 1848

SI Base Unit

SI Base Quantity

Discovered by Lord William Kelvin, 1848

SI Base Unit

SI Base Quantity

Discovered by Lord William Kelvin, 1848

SI Base Unit

SI Base Quantity

SI Base Unit

SI Base Quantity

SI Base Unit

SI Base Quantity

SI Base Unit

SI Base Quantity

SI Base Unit

SI Base Quantity

SI Base Unit

SI Base Quantity

SI Base Unit

SI Base Quantity

SI Base Unit

SI Base Quantity

SI Base Unit

SI Base Quantity

SI Base Unit

SI Base Quantity

SI Base Unit

SI Base Quantity

BASE UNITS

BASE · DERIVED
DECIMAL · BINARY · CONVERSION

BASE UNITS

BASE · DERIVED
DECIMAL · BINARY · CONVERSION

BASE UNITS

BASE · DERIVED
DECIMAL · BINARY · CONVERSION

BASE UNITS

BASE · DERIVED
DECIMAL · BINARY · CONVERSION

Discovered by
André-Marie Ampère, 1820

Discovered by
André-Marie Ampère, 1820

Discovered by
André-Marie Ampère, 1820

Discovered by
André-Marie Ampère, 1820

Discovered by
Jules Louis Gabriel Violle, 1881

Discovered by
Jules Louis Gabriel Violle, 1881

Discovered by
Jules Louis Gabriel Violle, 1881

Discovered by
Jules Louis Gabriel Violle, 1881

Discovered by
Lord William Kelvin, 1848

Discovered by
Lord William Kelvin, 1848

Discovered by
Lord William Kelvin, 1848

Discovered by
Lord William Kelvin, 1848

	Tesla, T SI Derived Unit
	Magnetic Flux Density SI Derived Quantity
	kg · s⁻² · A⁻¹ SI Base Expression
	This is the measurement for the strength of the magnetic field. One tesla is equal to one weber per square metre. A particle, that is carrying the charge of 1 coulomb, passing through a magnetic field of 1 tesla, perpendicular and at a speed of 1 metre per second, experiences a force of magnitude 1 newton. Named after Nicola Tesla

	Volt, V SI Derived Unit
	Electric Potential Difference, Electromotive Force SI Derived Quantity
	kg · m² · s⁻³ · A⁻¹ SI Base Expression
	This is the measurement for the strength of the magnetic field. One tesla is equal to one weber per square metre. A particle, that is carrying the charge of 1 coulomb, passing through a magnetic field of 1 tesla, perpendicular and at a speed of 1 metre per second, experiences a force of magnitude 1 newton. Named after Alessandro Giuseppe Antonio Anastasio Volta

	Watt, W SI Derived Unit
	Power, Radiant Flux SI Derived Quantity
	kg · m² · s⁻³ SI Base Expression
	This unit is defined as joule per second and is used to express the rate of energy conversion or transfer with respect to time. Named after James Watt

	Webber, Wb SI Derived Unit
	Magnetic Flux SI Derived Quantity
	kg · m² · s⁻² · A⁻¹ SI Base Expression
	This unit is defined as joule per second and is used to express the rate of energy conversion or transfer with respect to time.

	DECIMAL UNITS
	BASE · DERIVED DECIMAL · BINARY · CONVERSION

N	S	K	P	D
Yotta	Y	Septillion	10²⁴	1,000,000,000,000,000,000,000,000
Zetta	Z	Sextillion	10²¹	1,000,000,000,000,000,000,000
Exa	E	Quintillion	10¹⁸	1,000,000,000,000,000,000
Peta	P	Quadrillion	10¹⁵	1,000,000,000,000,000
Tera	T	Trillion	10¹²	1,000,000,000,000
Giga	G	Billion	10⁹	1,000,000,000
Mega	M	Million	10⁶	1,000,000
Kilo	k	Thousand	10³	1,000
Hecto	h	Hundred	10²	100
Deca	da	Ten	10¹	10
Unit	1	One	10⁰	1
Deci	d	Tenth	10^-1	0.1
Centi	c	Hundredth	10^-2	0.01
Milli	m	Thousandth	10^-3	0.001
Micro	μ	Millionth	10^-6	0.000'001
Nano	n	Billionth	10^-9	0.000'000'001
Pico	p	Trillionth	10^-12	0.000'000'000'001
Femto	f	Quadrillionth	10^-15	0.000'000'000'000'001
Atto	a	Quintillionth	10^-18	0.000'000'000'000'000'001
Zepto	z	Sextillionth	10^-21	0.000'000'000'000'000'000'001
Yocto	y	Septillionth	10^-24	0.000'000'000'000'000'000'000'001

	BINARY UNITS
	BASE · DERIVED DECIMAL · BINARY · CONVERSION

N	S	K	P	D
Yobi	Yi	Yottabinary	(2¹⁰)⁸	1,208,925,819,614,629,174,706,176
Zebi	Zi	Zettabinary	(2¹⁰)⁷	1,180,591,620,717,411,303,424
Exbi	Ei	Exabinary	(2¹⁰)⁶	1,152,921,504,606,850,000
Pebi	Pi	Petabinary	(2¹⁰)⁵	1,125,899,906,842,620
Tebi	Ti	Terabinary	(2¹⁰)⁴	1,099,511,627,776
Gibi	Gi	Gigabinary	(2¹⁰)³	1,073,741,824
Mebi	Mi	Megabinary	(2¹⁰)²	1,048,576
Kibi	Ki	Kilobinary	(2¹⁰)¹	1,024
Unit	1	One	(10⁰)	1

	CONVERSION UNITS
	BASE · DERIVED DECIMAL · BINARY · CONVERSION

	*SI Units* (French: Système International d'Unités) *Gaussian Units* (CGS: Centimetre-Gram-Second)
	Electric Charge, q 1 C (SI) = (10⁻¹ c) Fr (CGS)
	Electric Current, I 1 A (SI) = (10⁻¹ c) Fr/s (CGS)
	Electric Potential, φ · V 1 V (SI) = (10⁸ csup>−1) statV (CGS)
	Electric Field, E 1 V/m (SI) = (10⁶ c⁻¹) statV/cm (CGS)
	Magnetic Induction, B 1 T (SI) = (10⁴) Gs (CGS)
	Magnetic Field Strength, H 1 A/m (SI) = (4π 10⁻³) Oe (CGS)
	Magnetic Dipole Moment, μ 1 A·m² (SI) = (10³) erg/Gs (CGS)
	Magnetic Flux, Φ_m 1 Wb (SI) = (10⁸) Gs·cm² (CGS)
	Resistance, R 1 Ω (SI) = (10⁹ c⁻²) s/cm (CGS)
	Resistivity, ρ 1 Ω·m (SI) = (10¹¹ c⁻²) s (CGS)
	Capacitance, C 1 F (SI) = (10⁻⁹ c²) cm (CGS)
	Inductance, L 1 H (SI) = (10⁹ c⁻²) s²/cm (CGS)