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 today, 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.

The International System of Units (SI) is the only system of measurement units accepted worldwide and provides units for every type of measurement. As the UK’s National Metrology Institute, NPL is responsible for maintaining and developing the UK’s primary measurement standards for SI units and ensuring their comparability internationally.

In collaboration with the worldwide network of NMIs this activity not only ensures global measurement remains stable and comparable, but also allows society to have confidence in measurement data. As part of this, ensuring there are globally agreed prefixes as part of the SI, to use with measurement data, is essential for the effective communication of scientific information across technical disciplines.  

Dr Richard Brown, Head of Metrology at NPL, said: “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.

“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.”

Find out more about the SI Prefix expansion here