In the US and UK, numbers have a comma separating the thousands and a period separating the decimal portion.

The median round-trip time is 1,256,532.65 milliseconds.

In much of the EU, as well as Canada (both French- and English-speaking), numbers have a space separating the thousands and a comma separating the decimal portion.

The median round-trip time is 1 256 532,65 milliseconds.

In much of South America, numbers have a period separating the thousands and a comma separating the decimal portion.

The median round-trip time is 1.256.532,65 milliseconds.

India (specifically Hindi-speaking India) uses a format much like the US and UK, except (if I understand correctly) after the least-significant thousands grouping, additional groupings are by the hundreds. (I must admit, whenever I encounter this format, I tend to assume a digit got omitted unless I know the author's culture.)

The median round-trip time is 12,56,532.65 milliseconds.

In most cultures, the localized number format is used only when communicating in the native tongue (transitioning to the US/UK style when communicating in English). However, this is not universally true.

Of note: Canada is the only country I could find whose official language is English and whose number formatting conventions do NOT align with the US/UK convention. Edit: I've been informed in the comments that the US/UK system is the norm in Canada.

There may be other culture-specific Arabic-numeral number separator formats as well. These are the ones that I found in my research.

These numbering systems can usually be interpreted without knowing the author's culture, but sometimes there are ambiguities (such as the number "one and one one thousandth" vs "one thousand and one", both of which could be written as either "1,001" or "1.001", depending on culture). Sometimes these ambiguities can be deciphered from context within the rest of the answer/question, but sometimes not.

Is there a preferred format for numbers when writing question/answer content on English-language Stack Exchange sites, or is it okay to use whichever format is native to us?


@Rene has dug up a couple relevant links in the comments, I will summarize their relevance here.

What should the standard spelling be - British or US?

This discusses a preference between US and UK spellings of words like "favorite/favourite". The answer says that, for tags, the US spelling should be used. For body text, there is no official preference. For question titles, the most commonly used spelling should be used to increase search engine visibility.

Is it OK to change commas to narrow no-break spaces in numbers when editing a post?

This discusses editing questions to conform to a specific culture's number formatting. The answer says that one should not edit to conform to cultural standards unless there is an official preference, but stops short of saying whether there is such a preference for numbers.

Should the network use thousands separators in numbers?

I initially thought my question was a duplicate of this one, but this one discusses how numbers are displayed by the Stack Overflow software (in places like vote counts) rather than what formats are okay to use when writing question/answer content. The consensus on that question is that Stack Overflow should use US/UK number formatting, unless otherwise localized.

  • 1
    Eeek... Comments are not for extended discussion; this conversation has been moved to chat. – Journeyman Geek May 23 '20 at 1:01
  • this has been closed as a duplicate. i'm quite sure it isn't, and clearly explained the difference at the bottom of this post. shrug. oh well. – Woodrow Barlow May 24 '20 at 0:29

Write the separation pattern in a way that would both make sense to yourself as you apply it in your locale and to others who may not be in your locale. By and large this means you don't typically have to change anything.

However, if there is ambiguity, prefer English counting expressions. Stack Overflow's default language is English, so it's not unreasonable to expect that ambiguous expressions or phrases should prefer the English pronunciation.

That is to say, as an American I'm not bothered with the comma used for the decimal place. Life gets...interesting when dealing with crore and lakh though, but calculators exist to convert them if I have to.

  • the only time it would be truly ambiguous is for numbers with three digits of decimal precision, separated by a comma. and i imagine that usually this would be cleared up by the context of the rest of the answer. – Woodrow Barlow May 22 '20 at 17:01
  • @WoodrowBarlow with that much precision you probably don't go into the thousands anyway. I've never seen someone weigh 1.000,567 grams of sugar ;) – Luuklag May 22 '20 at 18:55
  • no, sorry, i meant numbers like "one and one one thousandth" vs "one thousand and one", both of which could be written as either "1.001" or "1,001" depending on culture. – Woodrow Barlow May 22 '20 at 18:58
  • @WoodrowBarlow: I've added a clarification to my answer. – Makoto May 22 '20 at 19:53
  • @Makoto i'm on board with this answer. :) i'm just going to wait a day before marking any answers. – Woodrow Barlow May 22 '20 at 19:57
  • As someone of indian origin... editing lakh and crore is helpful :D. – Journeyman Geek May 23 '20 at 13:20

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