# Use of unit abbreviations in Japanese

Are unit abbreviations like mm for millimetres or % for percent used in Japanese?
I've seen people translate those two words in to ミリメートル and パーセント respectively and that is what makes me raise this question.

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In what context? On exams and technical documents I've always seen them written as their abbreviated units (mm/cm, etc). While in novels (a non technical context) it would probably be more common to see them written in katakana. – Jeemusu Aug 23 '12 at 10:18
Both, since I want to know when and where each type are used – 小太郎 Aug 23 '12 at 10:21
I am hoping somebody else can add it a bit to this comment but, units do get dropped in some circumstances (possibly casual, possibly just when they are clear from context). Several years ago a teacher told my class 30degC was pronounced 30度. Initially she could not tell us how to say 30℃　：　she could not tell us, possiblY because she did not see how it would work. Tim – Tim Aug 23 '12 at 12:50
I don't think ３０度 exclusively referes to Celsius. Obviously it's most commonly used in that regard, but it could also be used to refere to a temperature in Degrees Centigrade, Fahrenheit, or Kelvin. All in the context of the situation I guess. – Jeemusu Aug 23 '12 at 14:05
30℃=摂氏３０度. People would rarely say that in Japan, though, since Celcius is the default. – dainichi Aug 23 '12 at 14:18

In written Japanese the abbreviations mm, kg, km, mg, cm, ml etc. are used as early as the second year of primary school. Their correct pronunciation is ミリメートル, キログラム, キロメートル, ミリグラム, センチメートル, ミリリットル respectively. In everyday language, mm and ml are abbreviated to ミリ (although ミリグラム seems to stay as is; see comments below), kg, km are abbreviated to キロ and cm to センチ.

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I can imagine the use of ミリグラム in daily conversation (e.g. when talking about medicines), but I cannot imagine the situation where one abbreviates ミリグラム to ミリ. I think that ミリグラム is too uncommon to make such abbreviation understandable. – Tsuyoshi Ito Aug 23 '12 at 18:36
Since we are on the topic of spoken abbreviations (which is off-topic to the question, I think), it is worth pointing out that パーセント is often shortened to パー (when the meaning is obvious enough). – Dave Aug 24 '12 at 2:30