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Metric Unit Prefixes

Prefixes of Base Units by Factors of Ten

By Todd Helmenstine

Scientific measurements are made using the metric system.

Scientific measurements are made using the metric system.

Siede Preis, Getty Images
Metric or SI (Le Système International d'Unités) units are based on units of ten. Very large or very small numbers are easier to work with when you can replace any scientific notation with a name.

For example: the distance from City A to City B is 8.0 x 103 meters. From the table, 103 can be replaced with the prefix 'kilo'. Now the distance could be stated as 8.0 kilometers or shortened further to 8.0 km.

The distance from Earth to the Sun is approximately 150,000,000,000 meters. You could write this as 150 x 109 m, 150 gigameters or 150 Gm.

The width of human hair runs on the order of 0.000005 meters. Rewrite this as 50 x 10-6m, 50 micrometers, or 50 μm.

 

Metric or SI prefixes
Prefix symbol x from 10x  
yotta Y 24 1,000,000,000,000,000,000,000,000
zetta Z 21 1,000,000,000,000,000,000,000
exa E 18 1,000,000,000,000,000,000
peta P 15 1,000,000,000,000,000
tera T 12 1,000,000,000,000
giga G 9 1,000,000,000
mega M 6 1,000,000
kilo k 3 1,000
hecto h 2 100
deca da 1 10
base   0 1
deci d -1 0.1
centi c -2 0.01
milli m -3 0.001
micro μ -6 0.000001
nano n -9 0.000000001
pico p -12 0.000000000001
femto f -15 0.000000000000001
atto a -18 0.000000000000000001
zepto z -21 0.000000000000000000001
yocto y -24 0.000000000000000000000001

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