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Reference guide

SI Prefixes

SI prefixes make units larger or smaller by powers of ten. They are used across length, mass, data, energy, pressure, power, and many other measurements.

Common smaller prefixes

Deci means one tenth, centi means one hundredth, milli means one thousandth, micro means one millionth, and nano means one billionth.

Common larger prefixes

Kilo means one thousand, mega means one million, giga means one billion, tera means one trillion, and peta means one quadrillion.

Why prefixes matter

A prefix changes the size of the unit without changing the type of measurement. For example, millimeter, centimeter, meter, and kilometer are all length units.

Data storage note

Data storage can use decimal prefixes such as KB and MB or binary prefixes such as KiB and MiB. Binary prefixes use powers of 1024 instead of 1000.

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