Physics reference
SI units
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PhysRef
A comprehensive table of the base SI units.
SI units.
unit symbol derivation base units quantity
ampere A — A electric current
becquerel Bq 1/s s-1 activity
candela cd — cd luminous intensity
coulomb C A s A s charge
farad F A s/V kg-1 m-2 s4 A2 capacitance
gray Gy J/kg m2 s-2 absorbed dose
henry H V s/A kg m2 s-2 A-2 inductance
hertz Hz 1/s s-1 frequency
joule J N m kg m2 s-2 energy
katal kat mol/s mol s-1 catalytic activity
kelvin [footnote 1] K — K temperature
kilogram kg — kg mass
lumen lm cd sr cd sr luminous flux
lux lx lm/m2 cd sr m-2 illumination
metre m — m length
mole mol — mol amount of substance
newton N kg m/s2 kg m s-2 force
ohm Ω (O) [footnote 2] V/A kg m2 s-3 A-2 resistance
pascal Pa N/m2 kg m-1 s-2 pressure
radian rad m/m 1 plane angle
second s — s time
siemens S 1/Ω (1/O) kg-1 m-2 s3 A2 electric conductance
sievert Sv J/kg m2 s-2 dose equivalent
steradian sr m2/m2 1 solid angle
tesla T Wb/m2 kg s-2 A-1 magnetic flux density
volt V W/A kg m2 s-3 A-1 voltage
watt W J/s kg m2 s-3 power
weber Wb V s kg m2 s-2 A-1 magnetic flux
Non-SI unit approved for use with SI.
unit symbol value in SI units
minute min 60 s
hour h 60 min = 3600 s
day d 24 h = 86 400 s
degree deg, ° (π/180) rad
arcminute arcmin, ' (1/60) deg = (π/10 800) rad
arcsecond arcsec, " (1/60)' = (π/648 000) rad
litre l, L, ℓ [footnote 3] 1 dm3 = 10-3 m3
tonne t 103 kg
electronvolt eV (1.602 177 33 +- 0.000 000 49) x 10-19 J
unified atomic mass unit u (1.660 540 2 +- 0.000 001 0) x 10-27 kg
nautical mile nm, nmi 1852 m
knot kn 1 nm/h = (1852/3600) m/s
angstrom Å (A*) [footnote 4] 10-10 m
are a 1 dam2 = 102 m2
hectare ha 104 m2
barn b 10-28 m2
bar bar 105 Pa
gal Gal 10-2 m/s2
curie Ci 3.7 x 1010 Bq
roentgen R 2.58 x 10-4 C/kg
rad rd, rad 10-2 Gy
rem rem 10-2 Sv
Legend.
unit
The name of the unit.

If this field is empty, then the unit has no special name in the SI standard. It must be represented as a composition of its more fundamental units.

symbol
The symbol for this unit.

If this field is empty, then the unit has no special name in the SI standard. It must be represented as a composition of its more fundamental units.

derivation
The most commonly-used composition of more fundamental units that is described as composing the unit.

If this field is empty, then the unit is either elementary or supplemental.

base units
The composition of base units that comprise the unit in question. This is a polynomial-like combination of the eight elementary and supplementary units: kg, m, s, A, K, rad, cd, and sr. These are always put in the form
kga mb sc Ad Ke radf cdg srh
If any of these a through h are zero, then the term is 1 and not shown.

If this field is empty, then the unit is either elementary or supplemental.

quantity
The name of the quantity the unit measures.
Footnotes.
1.
The unit kelvin replaces the unit degrees Kelvin. A temperature of absolute zero, for example, would be read "zero kelvins" and abbreviated 0 K, rather than "zero degrees Kelvin" and abbreviated 0 °K.

footnote 1
2.
The unit ohm is actually represented with a Greek capital letter Omega, but is often written in ASCII as O.

footnote 2
3.
A script, lowercase l was often used in the early days of the metric system to represent the litre, but such use is disfavored under SI. A capital L is preferred to a lowercase unadorned l, since it is easy for a lowercase l to be confused with the numeral 1.

footnote 3
4.
The symbol for the angstrom is actually represented with a capital letter A with a ring above it (Å), which is sometimes written incorrectly as an unadorned capital A.

footnote 4
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