Name
|
Symbol
|
Quantity
|
Equivalent SI unit
|
Widely used units expected to be used indefinitely
|
minute
|
min
|
time (SI unit multiple)
|
1 min = 60 s
|
hour
|
h
|
time (SI unit multiple)
|
1 h = 60 min = 3600 s
|
day
|
d
|
time (SI unit multiple)
|
1 d = 24 h = 1440 min = 86400 s
|
degree
|
°
|
plane angle (dimensionless unit)
|
1° = (π / 180) rad
|
minute
|
′
|
plane angle (dimensionless unit)
|
1′ = (1 / 60)° = (π / 10800) rad
|
second
|
″
|
plane angle (dimensionless unit)
|
1″ = (1 / 60)′ = (1 / 3600)° = (π / 648000) rad
|
hectare
|
ha
|
area (decimal unit multiple)
|
1 ha = 100 a = 10000 m2 = 1 hm2
|
litre
|
l or L
|
volume (decimal unit multiple)
|
1 L = 1 dm3 = 0.001 m3 = 1000 cc = 1000 cm3
|
tonne
|
t
|
mass (decimal unit multiple)
|
1 t = 103 kg = 1 Mg
|
Logarithmic units
|
neper
|
Np
|
level of a field quantity
|
LF = ln(F / F0) Np
|
|
|
level of a power quantity
|
LP = 1⁄2 ln(P / P0) Np
|
bel, decibel
|
B, dB
|
level of a field quantity
|
LF = 2 log10(F / F0) B
|
|
|
level of a power quantity
|
LP = log10(P / P0) B
|
Units with experimentally determined values
|
electronvolt
|
eV
|
energy
|
1 eV = 6981160217652999999♠1.60217653(14)×10−19 J
|
unified atomic mass unit dalton
|
u Da
|
mass
|
1 u = 1 Da = 6973166053886000000♠1.66053886(28)×10−27 kg
|
astronomical unit
|
ua[3][4][5]
|
length
|
1 ua = 7011149597870691000♠1.49597870691(6)×1011 米
|
Natural units (n.u.)
|
n.u. of speed (speed of light in vacuum)
|
c0
|
speed
|
7008299792458000000♠299792458 m/s (exact)[6]
|
n.u. of action (reduced Planck constant)
|
ħ
|
action
|
6966105457168000000♠1.05457168(18)×10−34 J·s
|
n.u. of mass (electron mass)
|
me
|
mass
|
6969910938260000000♠9.1093826(16)×10−31 kg
|
n.u. of time
|
ħ / mec02
|
time
|
6979128808866770000♠1.2880886677(86)×10−21 s
|
Atomic units (a.u.)
|
a.u. of charge (elementary charge)
|
e
|
electric charge
|
6981160217652999999♠1.60217653(14)×10−19 C
|
a.u. of mass (electron mass)
|
me
|
mass
|
6969910938260000000♠9.1093826(16)×10−31 kg
|
a.u. of action (reduced Planck constant)
|
ħ
|
action
|
6966105457168000000♠1.05457168(18)×10−34 J·s
|
a.u. of length, bohr (Bohr radius)
|
a0
|
length
|
6989529177210800000♠0.5291772108(18)×10−10 米
|
a.u. of energy, hartree (Hartree energy)
|
Eh
|
energy
|
6982435974417000000♠4.35974417(75)×10−18 J
|
a.u. of time
|
ħ / Eh
|
time
|
6983241888432650500♠2.418884326505(16)×10−17 s
|