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Comment by mdellabitta | Hacker News Reader

SI and metric are actually subtly different. Do any countries actually use SI rather than metric?

At least the whole EU uses SI units by Directive 80/181/EEC (so called "Units of Measure Directive"). From everything I know, most other countries of the world use SI as well. Not surprising, as the system is now 55 years old and explicitly replaced former definitions.

Even US laws explicitly refer to SI, for example the Metric Conversion Act of 1975: http://www.gpo.gov/fdsys/pkg/STATUTE-89/pdf/STATUTE-89-Pg100...

UK uses miles on road signs, pints in pubs, etc. Many people still use stones and pounds for human weight, even if they're in a medical setting.

However, those are explicitly defined in terms of SI units for use in the UK in that directive.

The question of GGP was, whether some countries use other metric systems which are not SI. I don't think such a country exists.

The Imperial volume units used in Britain are vaguely metric, and different from the US customary (i.e. Queen Anne) units. The Imperial gallon is the volume of 10 lb avoirdupois of water at s.t.p. The other similarity to French metric units is they replaced a number of different application-specific volume measures.

At about the same time as the Imperial unit reform Britain introduced the "florin" 2 shilling coin, 10 per pound, another vague attempt at decimalization.

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