In November 2022, measurement scientists and government representatives from around the world voted at the General Conference on Weights and Measures (CGPM) to expand the range of prefixes used within the International System of Units (SI).
This decision means that four new prefixes (two at the top end of the SI range and two at the bottom end of the SI range) can now be used to express measurements worldwide. This is the first expansion to the SI prefix range since 1991.
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What are the new SI prefixes and why do we need them?
The proposal, led by Prof Richard Brown, Head of Metrology at NPL, recommended the four new names.
The new names for very large numbers are:
They are joined by their tiny counterparts:
The change was largely driven by the growing requirements of data science and digital storage, which is already using prefixes at the top of the existing range (yottabytes and zettabytes, for expressing huge quantities of digital information). The prefixes for very small numbers are useful for quantum science and particle physics. However, these can be used with any SI unit, for example in the future we can be expected to talk about ronnametres and quettagrams.