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Analytical Chemistry

New prefixes for big numbers and small measurements

The additional names extend the range of official SI prefixes

by Ariana Remmel
December 1, 2022 | A version of this story appeared in Volume 100, Issue 43


Four numbers with corresponding labels that read: 1. 10^27 is ronna (R), 2. 10^30 is quetta (Q), 3. 10^-27 is ronto (r), 4. 10^-30 is quecto (q).

The International System of Units (SI) gained four prefixes at the 27th General Conference on Weights and Measures (CGPM) in Paris in November. The CGPM decided to expand the list of SI prefixes to encompass a larger range of numbers—both massive and minuscule. Now, ronna (R) and ronto (r) will describe multiplying factors of 1027 and 10–27, respectively. Quetta (Q) and quecto (q) go even further, to include factors of 1030 and 10–30, respectively. These codified SI prefixes will help data scientists accurately describe gargantuan quantities of digital information that are pushing the limits of the prefix yotta, for 1024, which has represented the upper range of the SI prefix list since it was adopted in 1991. The tiny complements of the freshly minted, behemoth prefixes also give chemists a new way to measure our smallest subunits. For example, the mass of an electron is approximately 1 rontogram, thanks to the updated list of SI prefixes.


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