Stop Putting Commas In Your Numbers

or Why you need to read Le Système international d’unités (8e édition)

How do you write very large or very small numbers? How, for example, would you write the speed of light out in full?

If you would write c = 299,792,458 m/s then please stop, because you’re doing it wrong. You can argue all you want about tradition, and “the way things have always been done” but you are still totally, absolutely, unequivocally wrong. There is a right way, an official, standardised way, to write very large and very small numbers, and it’s not with commas in them.

“Following the 9th CGPM (1948, Resolution 7) and the 22nd CGPM (2003, Resolution 10), for numbers with many digits the digits may be divided into groups of three by a thin space, in order to facilitate reading. Neither dots nor commas are inserted in the spaces between groups of three.”

The correct way to write the speed of light is c = 299 792 458 m/s. Ideally you’d use a special Unicode character, known as “NARROW NO-BREAK SPACE (U+202F)”, which stops text from wrapping around half-way through a number, but this isn’t very well supported, so the better-supported “THIN SPACE (U+2009)” or even just a normal space will do.

The reason for this is that the decimal point isn’t always a decimal point. Only 60% of countries use a full stop, whereas other countries use other marks. For example, a number that would traditionally be written in the UK as 123,456,789.01 would be written in France, Germany, Spain and many other countries as 123.456.789,01 and in Canada as either, depending on whether you’re working in English or French. This confusion (see this for example) was deemed undesirable and as such the scientific community declared in 2003 that:

The 22nd General Conference [of the BIPM],
considering that a principal purpose of the International System of Units is to enable values of quantities to be expressed in a manner that can be readily understood throughout the world …
reaffirms that “Numbers may be divided in groups of three in order to facilitate reading; neither dots nor commas are ever inserted in the spaces between groups”, as stated in Resolution 7 of the 9th CGPM, 1948.

Remember that thousand separators are also used when dealing with very small numbers. I’ve provided some examples below if you’re struggling to get your head around them.

Incorrect Correct Incorrect Correct
123 123 0.123 0.123
1234 1234 0.1234 0.1234
12,345 12 345 0.12345 0.123 45
123,456 123 456 0.123456 0.123 456
1,234,567 1 234 567 0.1234567 0.123 456 7
12,345,678 12 345 678 0.12345678 0.123 456 78

56 thoughts on “Stop Putting Commas In Your Numbers

  1. This is the funniest thread I’ve read in a long time. I’m so heartened that so many people feel strongly about establishing a precise standard for this. However, the degeneration into insults feels a bit like the current pro-vaxxer/anti-vaxxer zero-sum discourse. We need to do better as humans. Carry on, Mr Reid! I respect your work immensely.

  2. What’s the deal with the comments that have absolutely no vowels?

    Anyway, I have to agree with Mr. Reid and the CGPM because there needs to be one global standard, and the current use of two standards is untenable.

    To those who say that having a single global standard for commas vs. points is like forcing everyone in the world to use English, I say:
    1. It’s not the same thing,* and
    2. It is necessary to have a single global numerical standard to avoid the obvious confusion that results.

    For the same reason, those who say it’s okay to use the style applicable to where they are writing are wrong, because it fails to take into account the style standard of where the readers are READING.

    In today’s world, a person anywhere in the world can post a comment that can be read by a person anywhere ELSE in the world. This leads to confusion when there isn’t a global standard for the use of commas and points in writing numbers. Literally just TODAY I read a comment from someone who said “1.000 L”, and I thought he meant one liter, but in fact he meant one thousand liters. That’s a problem.

    For that reason, in addition to standardizing the use of spaces as number separators instead of commas or points, international standards bodies should also standardize the use of commas or points for decimal separators as well. I prefer the point rather than the comma, for various good reasons, but I’d be willing to convert if a different standard is agreed upon. But we need to HAVE a standard, because people around the world need to be able to communicate with each other without confusion or ambiguity.

    ________________________

    * It’s not the same thing, because when somebody writes in a language that’s foreign to you, it’s obvious. But when somebody writes a number using a comma instead of a point as a decimal, or a point instead of a comma (or space) as a digit separator, it is NOT necessarily obvious and can lead to confusion and serious errors.

  3. Pprntly, 70% f th wrld s wrng bcs t bthrs y.

    Ths s hlrs.

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