

UNITS OF THE INTERNATIONAL SYSTEM

The International System has
base units from
which all others in the system are derived.
The standards for the base units, except for the kilogram, are defined by
unchanging and reproducible physical occurrences. For example, the meter is defined as the distance traveled by
light in a vacuum in 1/299,792,458 of a second. The standard for the kilogram is a platinumiridium cylinder
kept at the International Bureau of Weights and Standards in Sèvres,
France. 
UNIT 
QUANTITY 
SYMBOL 
meter 
length 
m 
kilogram 
mass 
kg 
second 
time 
s 
ampere 
electric current 
A 
kelvin 
temperature 
K 
mole 
amount of matter 
mol 
candela 
luminous intensity 
cd 
The
International System uses two supplementary units that are based on
abstract geometrical concepts rather than physical standards. 
UNIT 
QUANTITY 
SYMBOL 
radian 
plane angles 
rad 
steradian 
solid angles 
sr 
Most of the units in the International System
are a derived unit, that is units defined in terms of base units and
supplementary units. Derived units
can be divided into two groups – those that have a special name and symbol,
and those that do not. 
WITH NAMES AND SYMBOLS 

MEASURE OF 
DERIVATION 
acceleration 
m/s^{2} 
angular acceleration 
rad/s^{2} 
angular velocity 
rad/s 
density 
kg/m^{3} 
electric field strength 
V/m 
luminance 
cd/m^{2} 
magnetic field strength 
A/m 
velocity 
m/s 
A
multiple of unit in the International System
is formed by adding a prefix to the name of that unit.
The prefixes change the magnitude of the unit by orders of 10 from_10^{18}_to_10^{18}.^{
}
For example, a kilometer is 1000 meters, a hectoliter is 100 liters, a milligram is 1/1000 of a gram, a megawatt is 1,000,000 watt, etc. 
PREFIX 
SYMBOL 
MULTIPLYING FACTOR 
exa 
E 
10^{18} = 1,000,000,000,000,000,000 
peta 
P 
10^{15} = 1,000,000,000,000,000 
tera 
T 
10^{12} = 1,000,000,000,000 
giga 
G 
10^{9}
= 1,000,000,000 
mega 
M 
10^{6}
= 1,000,000 
kilo 
K 
10^{3}
= 1,000 
hecto 
h 
10^{2}
= 100 
deca 
da 
10 =
10 
deci 
d 
10^{1}
= 0.1 
centi 
c 
10^{2}
= 0.01 
milli 
m 
10^{3}
= 0.001 
micro 
μ 
10^{6}
= 0.000,001 
nano 
n 
10^{9}
= 0.000,000,001 
pico 
p 
10^{12}
= 0.000,000,000,001 
femto 
f 
10^{15}
= 0.000,000,000,000,001 
atto 
a 
10^{18}
= 0.000,000,000,000,000,001 
^{ }
Listed below are a few of the
nonSI units
that are commonly used with the International System: 
UNIT 
QUANITY 
SYMBOL 
angstrom (=10.10m) 
length 
Å 
electronvolt (=0.160
aJ) 
energy 
eV 
hectare (=10,000 m^{2}) 
land
area 
ha 
liter (= 1.0 dm^{3}) 
volume
or capacity 
l 
standard atmosphere (=101.3
kPa) 
pressure 
atm 
UNIT 
MEASURE
OF 
SYMBOL 
DERIVATION 
coulomb 
electric charge 
C 
A ·s 
farad 
electric capacitance 
F 
A ·
s/V 
henry 
inductance 
H 
V ·s/A 
hertz 
frequency 
Hz 
cycles/s 
joule 
quantity of energy 
J 
N ·
m 
lumen 
flux of light 
lm 
cd · sr 
lux 
illumination 
lx 
lm/m^{2} 
newton 
fource 
N 
kg · m/s^{2} 
ohm 
electric resistance 
Ω 
V/A 
pascal 
pressure 
Pa 
N/m^{2} 
tesla 
magnetic flux density 
T 
Wb/
m^{2} 
volt 
voltage 
V 
W/A 
watt 
power 
W 
J/s 
weber 
magnetic flux 
Wb 
V ·s 
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