# SI prefixes

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.

Contents: SI prefix calculator and SI prefix table.

## SI prefix conversion calculator:

Enter the number in green field and click at "=" button:

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(result)

## 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..

Source: NIST.gov - prefixes. (retrieved 2017-04-18) 