New Metric Prefixes Get Bigger And Smaller


It always fascinates us that every single thing that is made had to be designed by someone. Even something as simple as a bag and box that holds cereal. Someone had to work out the dimensions, the materials, the printing on it, and assign it a UPC code. Those people aren’t always engineers, but someone has to think it out no matter how mundane it is before it can be made. But what about the terms we use to express things? Someone has to work those out, too. In the case of metric prefixes like kilo, mega, and pico, it is apparently the General Conference on Weights and Measures that recently had its 27th session. As a result of that, we have four more metric prefixes to learn: ronna, quetta, ronto, and quecto.

Apparently, the new prefixes are to accommodate “big data” which is rapidly producing more data than there are atoms in the Universe. There were actually proposed earlier in a slightly different form but accepted at the conference. Apparently quecca is too close to a Portuguese swear word. So what do these actually mean? A QB (quettabyte) would be 1030 bytes while an RB (ronnabyte) is only 1027.  So 1 QB would be 1,000,000 yottabytes (YB) the previous top of the scale.

On the other end of the scale, the previous tiny measure was the yocto. So a yW or yactowatt, would be 10-24 watts. A rw (rontowatt) is 10-27 and the qw or quectowatt is 10-30. The larger end of the scale seems more practical as now the sun weighs 2,000 quettagrams instead of 2,000,0000 yottagrams. In the old days, we used to mix prefixes like micro-micro farad instead of picofarad, so you could also say it was 2 mega-yottagrams, but that use has fallen out of favor in modern times.

We were sorry the earlier proposal by a student for ronna failed. The proposal would have had the prefix as “hella” as in a “hellawatt.” At least you’d remember it. Apparently, though, it wasn’t a serious contender because the new entries have to have a unique letter and they try to avoid things that measure common physical units although some of the older ones do. So hella, for example, clashes with both henry — the unit of inductance — and hecto, which is an existing prefix. If you write HW that’s a hectowatt, not a hellawatt. At least in ended in “a” and not “o” which indicates a positive power of 10 instead of a negative power, but that wasn’t enough to earn it a spot on the list.

Of course, the real politics in metrology isn’t the naming of things, but rather the definition of the units. Some people really get into that.



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