SI derived units
Other quantities, called derived quantities, are defined in terms of the seven base
quantities via a system of quantity equations. The SI derived units for these derived
quantities are obtained from these equations and the seven SI base units. Examples of
such SI derived units are given in Table 2, where it should be noted that the symbol 1
for quantities of dimension 1 such as mass fraction is generally omitted.
Table 2. Examples of SI derived units
SI derived unit
Derived quantity
area
volume
speed, velocity
acceleration
wave number
mass density
specific volume
current density
magnetic field strength
amount-of-substance concentration
luminance
mass fraction
Name
Symbol
square meter
m2
cubic meter
m3
meter per second
m/s
meter per second squared
m/s2
reciprocal meter
m-1
kilogram per cubic meter
kg/m3
cubic meter per kilogram
m3/kg
ampere per square meter
A/m2
ampere per meter
A/m
mole per cubic meter
mol/m3
candela per square meter
cd/m2
kilogram per kilogram, which kg/kg = 1
may be represented by the
number 1
For ease of understanding and convenience, 22 SI derived units have been given special
names and symbols, as shown in Table 3.
Table 3. SI derived units with special names and symbols
SI derived unit
Derived quantity
plane angle
solid angle
frequency
force
pressure, stress
energy,
work,
quantity of heat
power, radiant flux
electric
charge,
quantity of electricity
electric
potential
difference,
electromotive force
Name
Symbol
radian (a)
steradian (a)
hertz
newton
pascal
joule
rad
sr (c)
Hz
N
Pa
J
Expression
in terms of
other
SI
units
N/m2
N·m
Expression
in
terms
SI base units
watt
coulomb
W
C
J/s
-
m2·kg·s-3
s·A
volt
V
W/A
m2·kg·s-3·A-1
m·m-1 = 1 (b)
m2·m-2 = 1 (b)
s-1
m·kg·s-2
m-1·kg·s-2
m2·kg·s-2
of
capacitance
electric resistance
electric conductance
magnetic flux
magnetic flux density
inductance
Celsius temperature
farad
ohm
siemens
weber
tesla
henry
degree
Celsius
lumen
lux
a becquerel
F
S
Wb
T
H
°C
C/V
V/A
A/V
V·s
Wb/m2
Wb/A
-
m-2·kg-1·s4·A2
m2·kg·s-3·A-2
m-2·kg-1·s3·A2
m2·kg·s-2·A-1
kg·s-2·A-1
m2·kg·s-2·A-2
K
luminous flux
illuminance
activity
(of
radionuclide)
absorbed
dose, gray
specific
energy
(imparted), kerma
dose equivalent (d)
sievert
catalytic activity
katal
lm
lx
Bq
cd·sr (c)
lm/m2
-
m2·m-2·cd = cd
m2·m-4·cd = m-2·cd
s-1
Gy
J/kg
m2·s-2
Sv
kat
J/kg
m2·s-2
s-1·mol