Should large numbers be formatted with delimiters?

Question

Every country has a different way of delimiting large numbers. In USA, we put commas between every three digits. For example, one million would appear as 1,000,000. I believe this allows the reader to quickly deduce the magnitude of the number without tediously counting all the digits.

I have seen some prominent websites and apps forgo the delimiters, and thus they lose this benefit. The omission may or may not have been done on purpose. Are there any benefits for omitting delimeters? I would like to hear the standpoints of each side .

Instagram website has delimiters:

Instagram iPhone app does not have delimiters::

Answer 1

If you leave out the delimiter, then you also remove all doubt related to thousand-separator vs comma separator. Many countries use comma as decimal separator, so "10,000" could be interpreted as "10 comma 000".

I believe it depends on the circumstances. In general, the delimiter would increase readability, but sometimes the actual, exact number isn't that important.

There was a question about "correct payment in financial forms" a while ago - and in such tasks it's definitely important to get the numbers straight.

In other situations, you just want to know if the number is small, big or huge. Eg. a 4 digits of likes on Instagram is good. It's not that important whether it's 1234 or 7654 (because it's a lot more that my lousy 1 digit of likes anyway... ;-)

It's also possible to increase the "significance" of each digit by using different visual layouts and/or a postfix. Fewer digit, but obviously a higher value. Just like the Stack Exchange sites are doing. Even if I have more digits in the example below, it's easy to spot the king...

Vine uses this method too. By postfixing with "M" and "K", it's easy to identify 1.5M as a higher value than 274.9K. (This can be discussed, but lets just say that it's either intuitive for the user group, or that it's ok with a learning period to understand the convention).

Google could have done the same on their search results. It's a lot easier to read "1,000,000,000" than "1000000000" - but at the end of the day it's really not that important to know whether it's "1000000000" results or "100000" results (you never go beyond the first page anyway). I would be fine with "Wow, you need to refine your search term" and "I bet you'll find what you're looking for at this first page"...

Answer 2

Jørn's answer is pretty complete. Just to support it, and add a bit:

• It is easier to read numbers with delimiters - significants and scale are easily recognised that way.
• In the printed publishing world the delimiter ambiguity is solved by the use a half space character as a delimiter; on the web the same is known as thin space ( ). Like so: 1 234 000. Hair space is also sometimes used for this purpose.
• You may wish to have a look at the delimiters section of the Wikipedia's Style Guide. It promotes not using delimiters for 4 digit numbers.
• When the scale is important but not the precision, a unit system is used. Like 400k.
• Many web systems use localisation info to present the right delimiter. This can be:
  • IP based (the client IP determines the localisation).
  • User preference (like in many Google systems).
  • The site itself (such as www.amazon.de)
• If no localisation is available and there is a decimal point in numbers, style guides promote the use of the full stop as a decimal point (and thus the comma as a thousands separator).

My recommendations will be:

• Use delimiters for any number with 5 digits or more. (Obviously use it when decimal point exists.)
• When localisation is available: Use the correct delimiter character for the country.
• When localisation isn't available: Use thin space if precision is important, and unit system if it isn't.

Answer 3

If your users might do (e.g. copy & paste) something with the number, I wouldn’t use delimiters. When pasting the number into another system, any delimiters might be harmful: the system might only allow digits, or the system might use other delimiters (leading to a false interpretation of the number).

If you can’t know for certain where users are from, I wouldn’t use delimiters. You can’t deduce that users know the correct delimiter interpretation just because they understand/use a certain language.

Whenever I read a number with delimiters (in an international context), it takes me more time to decide how to interpret the delimiters than it would take me to interpret the number (without any delimiters) itself.