SI · CGS · accepted unitsRevised for the 2019 redefinition

MetricAtlas

Every metric unit worth knowing, from the kilogram to the barn: where each name comes from, how it was first defined, how it is defined now, and what it equals in imperial.

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Units
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Quantity groups
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SI base units
24
SI prefixes

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metric ⇄ imperial & US
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SI prefixes

quecto → quetta

Any metric unit takes these prefixes. Ronna, quetta, ronto and quecto were added in November 2022, the first new prefixes since 1991, largely because global data storage was heading toward the yottabyte.