The 20 SI prefixes are pre-symbols, used to form decimal multiples and submultiples of SI units. For example kilometre (km), kilo means a thousand times. Another example is millimetre (mm), where milli means thousandth part of something.
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SI prefix table
SI prefix tables contains 10+10 SI prefixes. First table contains multiple prefixes (they are bigger than base unit) and submultiple prefixes (smaller than base unit). You can find examples below tables:
Multiple prefixes:
Name
Symbol
Factor
yotta
Y
1024
zetta
Z
1021
exa
E
1018
peta
P
1015
tera
T
1012
giga
G
109
mega
M
106
kilo
k
103
hecto
h
102
deka
da
101
(base)
-
100=1
Examples:
1 hm = 1×102 m = 100 m
2 kN = 2×103 N = 2000 N
5 MHz = 5×106 Hz = 5 000 000 Hz
Submultiple prefixes:
Name
Symbol
Factor
(base)
-
100=1
deci
d
10-1
centi
c
10-2
milli
m
10-3
micro
µ
10-6
nano
n
10-9
pico
p
10-12
femto
f
10-15
atto
a
10-18
zepto
z
10-21
yocto
y
10-24
Examples:
1 cm = 1×10-2 m = 0.01 m
2 ms = 2×10-3 s = 0.002 s
5 µm = 5×10-6 m = 0.000001 m
Notice:
Multiple prefixes may not be used, in the case of the kilogram (SI base unit for mass) symbol already have prefix. Example: 10-6 kg = 1 mg and not 1 µkg (µ and k prefixes can not be used together in one unit)
Usage of prefixes which are not dividable with 103 (in tables with RED letters) is recommended only with few units (examples: hectoliter hL, hectopascal hPa, dekagram dg, centimetre cm..)
SI prefixes strictly represent powers of 10, they should not be used to represent powers of 2. Example, 1 kByte, is 1000 Byte and not 210 Byte = 1024 Byte. See also: binary prefixes..
