{"id":216,"date":"2025-08-30T17:15:07","date_gmt":"2025-08-30T15:15:07","guid":{"rendered":"https:\/\/sandrock.co.za\/carl\/?p=216"},"modified":"2025-08-30T17:15:18","modified_gmt":"2025-08-30T15:15:18","slug":"relative-frequency-of-si-units-and-prefixes","status":"publish","type":"post","link":"https:\/\/sandrock.co.za\/carl\/2025\/08\/relative-frequency-of-si-units-and-prefixes\/","title":{"rendered":"Relative frequency of SI units and prefixes"},"content":{"rendered":"\n

I am huge a fan of the SI system, but I’ve often noticed that even my academic colleagues take a mix-and-match aproach to the BIPM standards<\/a>. It is common for chemists to use \u00c5ngstrom over nanometre, and I don’t think I’ve ever seen anyone use megagram over tonne. <\/p>\n\n\n\n

Perhaps people are so used to mg (miligram) that they instinctively feel that Mg (megagram) would be confusing, and I admit Gg looks a bit weird. Is that a trend? Do people avoid repeated letters in their unit names? Mm (megameter) does feel a bit odd, although mm (milimeter) feels much more familiar.<\/p>\n\n\n\n

These questions drove me to quantify the relative frequency of the SI units and prefixes.<\/p>\n\n\n\n

Google search results<\/h2>\n\n\n\n

I used Google search results as a proxy for usage. I also tried the Google Ngram project<\/a>, but that turned out to be harder than I wanted it to be. After downloading all the data and parsing some of it, it didn’t contain all the terms I wanted.<\/p>\n\n\n\n

Here is the complete table showing log10(Google search results + 1) for every combination of the SI prefixes with the units mentioned in the SI brochure as base units or derived units. I’ve skipped degrees Celsius as the Google search API kept erroring on searches like “quettaCelsius”.<\/p>\n\n\n\n

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It’s always interesting when you get results like this – you can immediately start seeing some structure.<\/p>\n\n\n\n

These things jump out at me:<\/p>\n\n\n\n