Karandikars & Associates

SI Prefixes

The International System of Units, internationally known by the abbreviation SI (from French Système international d'unités), is the modern form of the metric system and the world's most widely used system of measurement. Coordinated by the International Bureau of Weights and Measures (abbreviated BIPM from French: Bureau international des poids et mesures) it is the only system of measurement with official status in nearly every country in the world, employed in science, technology, industry, and everyday commerce

The first General Conference on Weights and Measures (CGPM) approved the 8 prefixes for use, they were: deca, hecto, kilo, myria, deci, centi, milli, and myrio

In 1960, two prefixes were made obsolete: myria and myrio. Six prefixes were added. Three for forming multiples: mega, giga, and tera and three for forming submultiples: micro, nano, and pico

In 1964, two prefixes for forming submultiples were added: femto and atto. This created an imbalanced situation, where there were more prefixes for small quantities

In 1975, two prefixes for forming multiples were added: peta and exa

In 1991, four prefixes were added. Two for forming multiples: zetta and yotta. Two for forming submultiples: zepto and yocto

In 2022, four prefixes were added. Two for forming multiples: ronna and quetta. Two forming submultiples: ronto and quecto

BIPM is the international organization established by the Metre Convention in 1875, through which Member States act together on matters related to measurement science and measurement standards. Figure below picks up Factor, Name and Symbol of each of the prefixes, from BIPM