What is the correct abbreviation for Hour (with or without the full stop)? Since the last letter of the word is not same with the last letter of its abbreviation it should end with a period, right ? If so... why it is so common to use "h" without the full stop? Are they both correct ?

12 h


12 h.

closed as primarily opinion-based by tchrist Mar 26 '17 at 22:36

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  • This is largely a matter of style. Adhere to the discipline of your editor, publication, or organization, or in the absence of a house style, observe the guidance of the style manual of your preference. You have not indicated what kind of material you are writing, or how the duration will be used, but in general prose, my advice would be don't abbreviatetwelve hours is best. – choster Mar 26 '17 at 22:03

The abbreviation for hour is hr: (plural hrs) ​

written abbreviation for hour :

  • He ran the marathon in 2 hrs 48 mins. formal The plane departs at 15.00 hrs.

(Cambridge dictionary)


h: abbr.

  • hour



In this case, h is not an abbreviation, but a unit symbol. Like all other units - SI or otherwise - unit symbols do not have a '.'

If you explicitly need an abbreviation, I recommend you use hr. / hrs, which avoids confusion with the unit.

  • +1 Good answer. It's also worth noting that in French, times are written in 24-hours and use "h" rather than a colon, e.g. 2:30pm --> 14h30 – Dog Lover Mar 26 '17 at 22:15
  • But CDO (above) gives the example 'He ran the marathon in 2 hrs 48 mins.' Saying that this is the abbreviation rather than the unit symbol is splitting hairs. Also, Collins COBUILD Advanced English Dictionary states: << H or h is an abbreviation for words beginning with h, such as 'hour', 'height', 'hospital', and 'hard'. >> h is certainly the SI symbol for hours, but is also a more general abbreviation for hours. Full stops are not generally considered necessary after abbreviations in 'BrE'. – Edwin Ashworth Mar 26 '17 at 22:56

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