Forgive me if this has already been asked, I could not find it via search.

My question is this: what is the proper way to append computer storage abbreviations to a number? For example, a 500 gigabyte hard disk drive will usually be spelled as "500GB" on web sites, with no space, but occasionally I see "500 GB", with a space between the number and the unit. Putting a space between the number and the abbreviation makes more sense to me, but since even Apple does not put a space between them, I am not sure. Which is the proper way?

closed as primarily opinion-based by FumbleFingers, user66974, anongoodnurse, tchrist, Kristina Lopez Jun 9 '14 at 19:57

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.

  • Both usages are about equally common for nnn GB, which is obviously a relatively recent form. Something older, such as 100 mph, is much more likely to be written as two words. But there's no real concept of "correct" for such forms - choose whatever style guide you like, and follow their prescription. – FumbleFingers Jun 9 '14 at 17:10

It's a style matter.

This can make it a style-guide matter. Some style-guides insist on no space, some on a space.

Those that insist on a space generally don't have a space before the degree symbol for degrees of arc, or the prime and double prime when used for minutes, seconds, inches or feet, but do before the degree symbol when used for degrees of a scale (most often with temperature, e.g. 9 °C but 9° angle).

The space should be a non-breaking space so as to keep the unit on the same line as the number.

Some technical guides as well as writing guides have rules on the matter, so for example if you were writing to a guide that wanted no spaces, but also to a technical standard such as SI or NIST which insists on spaces, you would hence probably favour the space on the basis that if you are concerned with such a technical standard, then it—being more directly relate to the technical matters—would be of more importance to you.

Guides also differ on whether you would space, hyphenate, or close in the case of an adjectival use such as "10-m pole/10m pole/10 m pole". IIRC the SI standard both says you should use a space in such cases, and then actually hyphenates itself at another point!


As a matter of modern technical writing style, 500 gigabytes can be written as 500 GB or 500GB.

As a matter of grammar, fusing '500' and 'GB' into '500GB' makes as much sense to me as fusing '3' and 'apples' into '3apples'. I always separate numbers and the things that they count with a space.

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