Is using a comma as a number separator a cultural thing?
In the US, it's very common to add a comma for numbers of more than 3 digits (ex: 1,000 for one thousand ; 1,000,000 for one million ; etc.).
In France though, we don't use this at all and commas are used for decimal numbers only (ex: 2,46).
Do you know which countries are following the US rule, and which countries are not? Where can I find resources on this?
"Cultural" arguably. Countries tend to adopt guidelines for usage when they adopt their official numerical system. For example, when decimilization was adopted by Australia in the late 60s, the government published ways in which numbers would be written. The guides included notes regarding preferences from various institutions (eg. banks). In effect, they were publishing a style guide for the country. Many other modern states have done similar. FYI.
A part of the answer can found in this thread [International Currency Formatting Guidelines — Currency Codes] : http://ux.stackexchange.com/questions/9105/international-currency-formatting-guidelines-currency-codes
Most European countries have the comma as the decimal separator and the dot (period) as the thousand separator.
Isn't this simply a language-dependent thing? I think most European languages use dots and comma's the other way around compared to English. English 1,000,000.00 would in Dutch be 1.000.000,00. Sometimes one also has spacing: 1 000 000.00.
FWIW: In Switzerland we usually use apostrophes (i.e. 1'000'000.00). And IMO it's the best solution because people don't mistake it for a decimal mark.
This is a common problem in localization (`l10n`) and internationalization (`i18n`).
@gef05: Did Australians not use the decimal point at all before the introduction of decimal currency? Even if were less common, wouldn't it still have been needed for exchange rates (e.g., A£1 = US$2.24) or maths textbooks (π = 3.14159265359...)?
@gerrit: Not just language-dependent as it turns out. For the decimal point South African English (officially) uses the comma but USA, UK, and Australian English all use the period. I only just found this out.
- In Albania, Belgium, Bosnia, Estonia, France, Finland, Hungary, Poland, Czech Republic, Slovakia and much of Latin Europe as well as French Canada: 1 234 567,89 (In Spain, in handwriting it is also common to use an upper comma: 1.234.567'89)
- In Brazil, Germany, Netherlands, Denmark, Italy, Portugal, Romania, Sweden, Slovenia, Greece and much of Europe: 1 234 567,89 or 1.234.567,89. In handwriting, 1˙234˙567,89 is also seen, but never in Denmark, the Netherlands, Portugal, Sweden or Slovenia. In Italy a straight apostrophe is also used in handwriting: 1'234'567,89.
- In Switzerland: There are two cases. 1'234'567.89 is used for currency values. An apostrophe as thousands separator along with a "." as decimal symbol. For other values the SI style 1 234 567,89 is used with a "," as decimal symbol. When handwriting, a straight apostrophe is often used as the thousands separator for non-currency values: 1'234'567,89.
- In English Canada, Ireland, Israel, Japan, Korea (both), Malaysia, New Zealand, Singapore, Taiwan, Thailand, the Philippines, the United Kingdom, and the United States: 1,234,567.89 or 1,234,567·89; the latter is generally found only in older, and especially handwritten, documents. Australia used this style up until the 1970s; now it uses the SI style.
- SI style: 1 234 567.89 or 1 234 567,89 (in their own publications the dot is used in the English version and the comma in the French version).
- In China, comma and space are used to mark digit groups because dot is used as decimal mark. There is no universal convention on digit grouping, so both thousands grouping and no digit grouping can be found. However, grouping can also be done every four digits: 123,4567.89, since names for large numbers in Chinese are based on powers of 10,000 (e.g. the next new word is for 108). Japan is similar.
- In Mexico: 1'234,567.89; for million separator an apostrophe is used.
- In India, due to a numeral system using lakhs (lacs) (1,00,000 equal to 100 000) and crores (1,00,00,000 equal to 10 000 000), comma is used at levels of thousand, lakh and crore, for example, 10 million (1 crore) would be written as 1,00,00,000.
To prevent linkrot, could you describe the conclusions from the resource you're linking to, rather than just pointing at it?
In Canada, some English sources (such as every math textbook I've ever seen) will also use spaces instead of commas, although most people use commas in their regular usage.