Metric prefix

A metric prefix is a <a href="/facts/Unit_prefix/CTotM82r">unit prefix</a> that precedes a basic unit of measure to indicate a <a href="/facts/Multiple_(mathematics)/tkte6NXa">multiple or submultiple</a> of the unit. All metric prefixes used today are <a href="/facts/Decimal/7omfVNIM">decadic</a>. Each prefix has a unique symbol that is prepended to any unit symbol. The prefix <a href="/facts/Kilo-/akxTdXyp">kilo</a>, for example, may be added to gram to indicate multiplication by one thousand: one <a href="/facts/Kilogram/lU2zbPk8">kilogram</a> is equal to one thousand grams. The prefix <a href="/facts/Milli-/h1TVNfuW">milli</a>, likewise, may be added to metre to indicate division by one thousand; one millimetre is equal to one thousandth of a metre.
Decimal multiplicative prefixes have been a feature of all forms of the <a href="/facts/Metric_system/to24H0YK">metric system</a>, with six of these dating back to the system's introduction in the 1790s. Metric prefixes have also been used with some non-metric units. The SI prefixes are metric prefixes that were standardised for use in the <a href="/facts/International_System_of_Units/S7YLglNz">International System of Units</a> (SI) by the <a href="/facts/International_Bureau_of_Weights_and_Measures/tPEu4X0s">International Bureau of Weights and Measures</a> (BIPM) in resolutions dating from 1960 to 2022. Since 2009, they have formed part of the <a href="/facts/ISO%2fIEC_80000/k1nrIjMW">ISO/IEC 80000</a> standard. They are also used in the <a href="/facts/Unified_Code_for_Units_of_Measure/qF8tqubR">Unified Code for Units of Measure</a> (UCUM).

Metric prefix open-in-new

Metric prefix