
International System of Units
Definitions of SI Base Units
 Meter
 The meter is the length of path travelled by light in vacuum
during a time interval of 1/299 792 458 of a second (17th CGMP,
1983).
 Kilogram
 The kilogram is the unit of mass: it is equal to the mass of
the international prototype of the kilogram (3rd CGMP, 1901)
 Second
 The second is the duration of 9 192 631 770 periods of the
radiation corresponding to the transition between the two hyperfine
levels of the ground state of the cesium133 atom (13th CGMP,
1967).
 Ampere
 The ampere is that constant current which, if maintained in two
straight parallel coductors of infinite length, of negligible
circular crosssection, and placed 1 meter apart in vacuum, would
produce between these conductors a force equal to 2 x
10^{7} newton per meter of length (9th CGPM, 1948)
 Kelvin
 The kelvin, unit of thermodynamic temperature, is the fraction
1/273,16 of the thermodynamic temperature of the triple point of
water (13th CGMP)
 Mole
 The mole is the amount of substances of a system which contains
as many elementary entities as there are atoms in 0,012 kilogram of
carbon12. When the mole is used, the elementary entities must be
specified and may be atoms, molecules, ions, electrons, other
particles, or specific groups of such particles (14th
CGPM,1971).
 Candela
 The candela is the luminous intensity, in a given direction, of
a source that emits monochromatic radiation of frequency 540 x
10^{12} hertz and that has a radiant intensity in that
direction of (1/683) watt per steradian (16th CGPM, 1979).
Names and Symbols for the SI Base Units
Physical quantity 
Name of SI unit 
Symbol for SI unit 
length 
meter 
m 
mass 
kilogram 
kg 
time 
second 
s 
electric current 
ampere 
A 
thermodynamic temperature 
kelvin 
K 
amount of substance 
mole 
mol 
luminous intensity 
candela 
cd 
SI Derived Units with Special Names and Symbols

Name of 
Symbol for 
Expression in 
Physical Quantity 
SI unit 
SI Unit 
terms of SI base units 
frequency 
hertz 
Hz 
s^{1} 
force 
newton 
N 
m kg s^{2} 
pressure, stress 
pascal 
Pa 
N m^{2} 
= m^{1} kg s^{2} 
energy, work, heat 
joule 
J 
N m 
= m^{2} kg s^{2} 
power, radiant flux 
watt 
W 
J s^{1} 
= m^{2} kg s^{3} 
electric charge 
coulomb 
C 
A s 
electric potential, 
volt 
V 
J C^{1} 
= m^{2} kg s^{3} A^{1} 
(electromotive force) 
electric resistance 
ohm 
W 
V A^{1} 
= m^{2} kg s^{3} A^{2} 
electric conductance 
siemens 
S 
W^{1} 
= m^{2} kg^{1} s^{3}
A^{2} 
electric capacity 
farad 
F 
C V^{1} 
= m^{2} kg^{1} s^{4}
A^{2} 
magnetic flux density 
tesla 
T 
V s m^{2} 
= kg s^{2} A^{1} 
magnetic flux 
weber 
Wb 
V s 
= m^{2} kg s^{2} A^{1} 
inductance 
henry 
H 
V A^{1} s 
= m^{2} kg s^{2} A^{2} 
Celsius temperature 
degree Celsius 
°C 
K 
luminous flux 
lumen 
lm 
cd sr 
illuminance 
lux 
lx 
cd sr m^{2} 
activity (radioactice) 
becquerel 
Bq 
s^{1} 
absorbed dose (of radiation) 
gray 
Gy 
J kg^{1} 
= m^{2} s^{2} 
dose equivalent 
sievert 
Sv 
J kg^{1} 
= m^{2} s^{2} 
(dose of equivalent index) 
plane angle 
radian 
rad 
1 
= m m^{1} 
solid angle 
steradian 
sr 
1 
= m^{2} m^{2} 
SI Prefixes
Factor 
Prefix 
Symbol 

Factor 
Prefix 
Symbol 
10^{24} 
yotta 
Y 

10^{1} 
deci 
d 
10^{21} 
zetta 
Z 

10^{2} 
centi 
c 
10^{18} 
exa 
E 

10^{3} 
milli 
m 
10^{15} 
peta 
P 

10^{6} 
micro 
m 
10^{12} 
tera 
T 

10^{9} 
nano 
n 
10^{9} 
giga 
G 

10^{12} 
pico 
p 
10^{6} 
mega 
M 

10^{15} 
femto 
f 
10^{3} 
kilo 
k 

10^{18} 
atto 
a 
10^{2} 
hecto 
h 

10^{21} 
zepto 
z 
10^{1} 
deca 
da 

10^{24} 
yocto 
y 
© 10.02.2003 by Florian Häußermann. No rights
reserved.
