physical quantity 
common
symbols 
name of
unit 
symbol
for unit 
unit
expressed in base units 
unit
expressed in other SI units 
Length, Distance 
l,d,r,x,y,z,s 
meter 
m 
Base Unit * 

Area 
A 

m^{2} 


Volume 
V 

m^{3} 

1000 liters 
Mass 
m 
kilogram 
kg 
Base Unit 

Time 
t 
second 
s 
Base Unit 

Density 
r 

kg/m^{3} 


Angle 
q, f 
radian 
rad 
arc length/radius 
(see note 9) 
Temperature 
T 
kelvin 
K 
Base Unit 
(see note 9) 
Velocity 
v, u, v 

m/s 


Acceleration 
a, a 

m/s^{2} 


Angular Velocity 
w 
(see note 10) 
rad/sec 
1/s, or s^{1} 

Angular
Acceleration 
a 

1/s^{2} or s^{2} 


Momentum 
p, p 

kg m/s 


Frequency 
n, f 
hertz 
Hz 
1/s or s^{1} 

Angular
Frequency 
w 
(see note 10) 
1/s or s^{1} 


Period 
T, t 

s 


Wavelength 
l 

m 


Force 
F, F 
newton 
N 
kg m/s^{2} 

Torque 
T, t, G 
(see note 11) 
N m 
kg m^{2}/s^{2} 

Moment of
Inertia 
I 

kg m^{2} 


Angular Momentum 
L, L 

kg m^{2}/s 


Work, Energy,
Heat 
W,K,E,U,Q 
joule 
J 
kg m^{2}/s^{2} 
N m 
Power 
P 
watt 
W 
kg m^{2}/s^{2} 
J/s 
Pressure 
p 
pascal 
Pa 
kg/m s^{2} 
N/m^{2} 
Density 
r 

kg/m^{2} 


Specific Heat 
c 

J/kg K 


Current 
I 
ampere 
A 
Base Unit 

Charge 
q, Q 
coulomb 
C 
A sec 

Volume Charge
Density 
r 

C/m^{2} 
A sec/m^{2} 

Surface Charge
Density 
s 

C/m^{2} 
A sec/m^{2} 

Linear Charge
Density 
l 

C/m 
A sec/m 

Electric
Potential 
V, F 
volt 
V 
kg m^{2}/A s^{3} 
W/A 
Resistance 
R 
ohm 
W 
kg m^{2}/A^{2} s^{3} 
V/A 
Capacitance 
C 
farad 
F 
A^{2} s^{2}/kg m^{2} 
C/V 
Inductance 
L 
henry 
H 
kg m^{2}/A^{2} s^{2} 
Wb/A 
Electric Field 
E 

N/C 
kg m/A s^{3} 

Electric
Displacement 
D 

C/m^{2} 


Electric
Polarization 
P 

C/m^{2} 


Magnetic Flux 
F 
weber 
Wb 
kg m^{2}/A s^{2} 
V s 
Magnetic
Induction 
B 
tesla 
T 
kg/A s^{2} 
N/A m 
Magnetic Field 
H, B 
(see note 12) 
A/m 


Magnetization 
M 

A/m 


*In 1983 the speed of light was fixed, effectively making m/s a base
unit and m a derived unit. However, this difference is not important for our purposes.
Some Usage Notes on Symbols for Physics Units and Quantities
 Scalar quantities are expressed in italic
script, like "x, d, s, T, . . ."
 Vector quantities are expressed in bold
script, like "v, a, F, . . .". In handwriting, vectors are
indicated by putting an arrow over the symbol . Vector magnitudes are italic and not bold,
or with no arrow over them: "v, a, F, . . ."
 Greek letters "w, q, a, F. . . "
are used for angular measurements and also for many other quantities. The same conventions
for italic scalars and bold vectors apply to Greek letters.
 There is no special meaning to the choice
of capital or lowercase letters for quantity symbols, but the common usage should be
followed. For example, t is usually used for time,
but T is used for temperature.
 Unit symbols are only capitalized if they
are named after a person. Example: g (grams), N (newtons)
 Capitalization is very important in metric
prefixes: compare milli (m) and Mega (M).
 The names of units are not
capitalized, even if the symbol for it is: newton (N). If we capitalize it
("Newton"), then we are talking about the man, not the unit.
 The only SI units that have a symbol
consisting of more than one letter are pascals (Pa) and webers (Wb). Note the
capitalization.
 Angle and
Temperature are dimensionless quantities. Their units are really just labels and do not
have any algebraic value. Including them in a result is not mathematically required (but
is usually advised for the sake of clarity). Ex: 5 rad/sec = 5 sec^{1}
^{ }
 A hertz (Hz)
is only used in conjunction with ordinary frequencies (cycles per second or revolutions
per second). Although it is dimensionally equivalent to 1/seconds, it is never used for
angular frequency or angular velocity.
 Similarly,
the units for torque (N m) are dimensionally equivalent to the units for work and energy
(joules), but joules are strictly a unit of energy and we never use them as a unit of
torque. Torque is just left as newtonmeters.
 There is some confusion in textbooks about
the use of "B" for either the magnetic field or the magnetic induction.
Some authors mean "magnetic induction" when they say "magnetic field".
Use the convention adopted by the particular book that you are using.
