Help Me Ronna! New SI Prefixes Adopted

On 2022-11-18, the Bureau international des poids et mesures (BIPM, International Bureau of Weights and Measures) adopted the first expansion of the prefixes used to scale SI units to larger and smaller values. This is the first expansion since 1991 when zetta, yotta, zepto, and yocto were added to accommodate science at the molecular and atomic scale and as an apparent tribute to the Marx brothers.

This time, one of the motivations for expansion was computing and “big data”, where a yottabyte may be a lotta bytes today, but not necessarily in a few years.

And so, we now have:

  • quecto 10^{-30}
  • ronto 10^{-27}
  • ronna 10^{27}
  • quetta 10^{30}

The mass of the electron is about one rontogram, Jupiter weighs around two quettagrams, and the diameter of the observable universe (depending on how you define it) is roughly one ronnameter.

In 2004, in “Yotta Yotta Universe”, I observed that SI prefixes were not up to talking about many things in Planck units. They still aren’t. While back then I expressed the radius of the universe as around 8 mega mega yotta yotta Planck lengths, now you can write it as just 8 quetta quetta Planck lengths.

These new prefixes used up the last two Latin alphabet letters not used by existing units or prefixes. They’ll have to get creative the next time they expand.


By default, this entire enterprise is racist, misogynistic and lgbtq±phobic, likely perpetrated by cis-hetero-privileged WM’s who continue to appropriate Latin for their nefarious non-diverse, non-gender-affirming purposes. Science is sooo exclusionary! And, to add insult to injury, where are the pronouns? Speaking of all that oppression, Happy Thanksgiving!


The prefixes need more DIE (diversity, inclusion, and equity). They were all made up by dead white men. Decolonize the prefixes! Instead of quetta, use wakanda.


The original proposal to the BIPM used “quecca” for 10^{30} and this was cited in several articles until somebody pointed out that “queca” is the F-bomb in Portuguese. Well, the colonialists couldn’t have that, so “quetta” it became.

Other proposals were “bronto” or “hella” for 10^{27}. I don’t know if “bronto” influenced “ronto” and “ronna”.