First update to the SI prefixes since 1991

Measurement scientists and government representatives from around the world at the General Conference on Weights and Measures (CGPM) in Versailles, France earlier this month voted to expand the range of prefixes within the International System of Units (SI).

Dr Richard Brown, head of metrology at the National Physical Laboratory (NPL), the UK’s national metrology institute, led the proposal recommending the new names – ronna and quetta – as SI prefixes for 1027 and 1030, respectively. They are joined by their microscopic counterparts, ronto for 10−27 and quecto for 10−30. The proposal was approved by the CGPM and these new prefixes have been incorporated into the SI with immediate effect, becoming the first expansion to the range of SI prefixes since 1991.

The expansion has been driven by the requirements of data science, digital storage and the exponentially growing size of the global datasphere, which is already using prefixes at the top of the existing scale. Additionally, the prefixes for very small numbers are useful for quantum science and particle physics.

“Our system of SI prefixes has expanded over the years in response to advances in science and technology requiring access to an increased range of orders of magnitude relating to measurement,” explains Brown. “This most recent change is essential to meet the requirements of data science and the ever-growing global datasphere – growth that we expect to accelerate with more widespread digitalisation and the advent of new technologies, such as quantum computing. These new SI prefixes will allow clear and unambiguous communication of these measurements for many years to come.”
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