API
SI Base Units and Associated Constants
Unit |
Unit symbol |
Quantity |
Associated constant |
Associated constant name |
Associated constant value |
|---|---|---|---|---|---|
|
\(\text{s}\) |
time |
|
Hyperfine transition frequency of Cs |
\(\Delta\nu_\text{Cs}=9192631770~\text{Hz}\) |
|
\(\text{m}\) |
length |
|
Speed of light |
\(c=299792458~\frac{\text{m}}{\text{s}}\) |
|
\(\text{kg}\) |
mass |
|
Planck constant |
\(h=6.62607015\times 10^{-34}~\text{J}\cdot\text{s}\) |
|
\(\text{A}\) |
electric current |
|
Elementary charge |
\(e=1.602176634\times 10^{-19}~\text{C}\) |
|
\(\text{K}\) |
thermodynamic temperature |
|
Boltzmann constant |
\(k_\text{B}=1.380649\times 10^{-23}~\frac{\text{J}}{\text{K}}\) |
|
\(\text{mol}\) |
amount of substance |
|
Avogadro constant |
\(N_\text{A}=6.02214076\times 10^{23}~\text{mol}^{-1}\) |
|
\(\text{cd}\) |
luminous intensity |
|
Luminous efficacy of \(540~\text{THz}\) radiation |
\(K_\text{cd}=683~\frac{\text{lm}}{\text{W}}\) |
Derived Units
Unit |
Unit symbol |
Quantity |
Definition |
|---|---|---|---|
|
\(\text{Hz}\) |
frequency |
\(\text{s}^{-1}\) |
|
\(\text{N}\) |
force; weight |
\(\text{kg}\frac{\text{m}}{\text{s}^2}\) |
|
\(\text{Pa}\) |
pressure; stress |
\(\frac{\text{N}}{\text{m}^2}\) |
|
\(\text{J}\) |
energy; work; heat |
\(\text{N}\text{m}\) |
|
\(\text{W}\) |
power; radiant flux |
\(\frac{\text{J}}{\text{s}}\) |
|
\(\text{C}\) |
electric charge |
\(\text{A}\text{s}\) |
|
\(\text{V}\) |
electrical potential difference |
\(\frac{\text{W}}{\text{A}}\) |
|
\(\text{F}\) |
capacitance |
\(\frac{\text{C}}{\text{V}}\) |
|
\(\text{Ω}\) |
resistance; impedance; reactance |
\(\frac{\text{V}}{\text{A}}\) |
|
\(\text{S}\) |
electrical conductance |
\(\text{Ω}^{-1}\) |
|
\(\text{Wb}\) |
magnetic flux |
\(\text{V}\text{s}\) |
|
\(\text{T}\) |
magnetic flux density |
\(\frac{\text{Wb}}{\text{m}^2}\) |
|
\(\text{H}\) |
inductance |
\(\frac{\text{Wb}}{\text{A}}\) |
Additional Units
For convenience, a number of commonly used units that are not directly combinations of SI base units is also included. These constants simplify the specification of properties, that are not given in SI units. However, as the representation of quantities is unique, they do not appear in formatted outputs.
Unit |
Unit symbol |
Quantity |
Definition |
|---|---|---|---|
|
\(\text{Å}\) |
length |
\(10^{-10}~\text{m}\) |
|
\(\text{u}\) |
mass |
\(1.6605390671738466\times 10^{-27}~\text{kg}\) |
|
\(\text{au}\) |
length |
\(149597870700~\text{m}\) |
|
\(\text{bar}\) |
pressure |
\(10^5~\text{Pa}\) |
|
\(\text{cal}\) |
energy |
\(4.184~\text{J}\) |
|
\(\text{d}\) |
time |
\(86400~\text{s}\) |
|
\(\text{De}\) |
dipole moment |
\(\sqrt{10^{-19}~\text{JÅ}^3}\) |
|
\(^\circ\) |
angle |
\(\frac{\pi}{180}~\text{rad}\) |
|
\(\text{g}\) |
mass |
\(10^{-3}~\text{kg}\) |
|
\(\text{h}\) |
time |
\(3600~\text{s}\) |
|
\(\text{l}\) |
volume |
\(10^{-3}~\text{m}^3\) |
|
\(\text{min}\) |
time |
\(60~\text{s}\) |
|
\(\text{rad}\) |
angle |
Additional Constants
Constant |
Name |
Symbol |
Value |
|---|---|---|---|
|
Gravitational constant |
\(G\) |
\(6.6743\times 10^{-11}~\frac{\text{m}^3}{\text{kg}\cdot\text{s}^2}\) |
|
Ideal gas constant |
\(R=N_\text{Av}k_\text{B}\) |
\(8.31446261815324~\frac{\text{J}}{\text{mol}\cdot\text{K}}\) |
Prefixes
All units can be combined with the following prefixes:
Prefix |
Prefix symbol |
Value |
Prefix |
Prefix symbol |
Value |
|---|---|---|---|---|---|
|
\(\text{d}\) |
\(10^{-1}\) |
|
\(\text{da}\) |
\(10^{1}\) |
|
\(\text{c}\) |
\(10^{-2}\) |
|
\(\text{h}\) |
\(10^{2}\) |
|
\(\text{m}\) |
\(10^{-3}\) |
|
\(\text{k}\) |
\(10^{3}\) |
|
\(\text{µ}\) |
\(10^{-6}\) |
|
\(\text{M}\) |
\(10^{6}\) |
|
\(\text{n}\) |
\(10^{-9}\) |
|
\(\text{G}\) |
\(10^{9}\) |
|
\(\text{p}\) |
\(10^{-12}\) |
|
\(\text{T}\) |
\(10^{12}\) |
|
\(\text{f}\) |
\(10^{-15}\) |
|
\(\text{P}\) |
\(10^{15}\) |
|
\(\text{a}\) |
\(10^{-18}\) |
|
\(\text{E}\) |
\(10^{18}\) |
|
\(\text{z}\) |
\(10^{-21}\) |
|
\(\text{Z}\) |
\(10^{21}\) |
|
\(\text{y}\) |
\(10^{-24}\) |
|
\(\text{Y}\) |
\(10^{24}\) |
|
\(\text{r}\) |
\(10^{-27}\) |
|
\(\text{R}\) |
\(10^{27}\) |
|
\(\text{q}\) |
\(10^{-30}\) |
|
\(\text{Q}\) |
\(10^{30}\) |