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Well-known game journalists TotalBiscuit and Jim Sterling use [the number of frames per second] fps instead of 30FPS or 30 FPS, without an intervening space between the units and the following units (like 30fps or 60fps).

Example One


PC users will be delighted to know it’s [the game] locked at 30fps on all platforms.

Example Two


24fps lock
30fps lock

In my opinion 30 FPS (with space) is correct. Who is right?

marked as duplicate by Hot Licks, NVZ, tchrist Aug 27 '16 at 20:10

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    With the exception of some scientific terms, whether such abbreviations are expressed in lower-case or upper-case is an editorial policy. – Hot Licks Aug 27 '16 at 17:47
  • What makes you think there's such a thing as a "correct spelling" that applies here? I can easily think of six perfectly reasonable possibilities without even trying. Why would any of those be worthy of the Royal English Academy's highly sought Impeccable Imprimatur of Correctness by the Grace of Her Majesty Elizabeth I and II, Regina, that all others might be cast into the shame everlasting of incorrigible disrepute whence corrigenda come never? :) – tchrist Aug 27 '16 at 17:49
  • @HotLicks: How about space? – user598527 Aug 27 '16 at 17:52
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    Spacing is also editorial policy. – Hot Licks Aug 27 '16 at 17:54
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    It seems to me that this question is a partial duplicate of the cited earlier question (the part concerned with whether there should be a space between the number and the unit of measure) but partly a completely different question (the part about whether the units of measure for the abbreviation fps should be capped or lowercase). Also, I don't think that the earlier question—or any of the answers there—looked at "rate" units of measure as a separate subcategory of units of measure that might have their own informal but consistent rules of usage. – Sven Yargs Aug 28 '16 at 22:33

As various commenters have noted above, the choices of whether to capitalize or lowercase rpm/RPM and whether to close up or include a letter space between the number and the unit of measure are style issues to be determined by style guide, house style rules, or (in a vacuum) lonely authors.

Nevertheless some trends are discernible in historical published instances of three similar abbreviations of rates: miles per hour (mph/MPH), revolutions per minute (rpm/RPM) and frames per second (fps/FPS).

Starting with "miles per hour," I ran test for four forms: "60 mph" (blue line), "60mph" (red line), 60 MPH (green line), and 60MPH (yellow line) for the period 1900–3005. This chart shows the case-sensitive results:

Ngram shows the case-insensitive results (which reduce the four lines to two—with and without the letter space) for the same data here: Ngram graph

For "revolutions per minute," here is the corresponding case-sensitive chart for "45 rpm" (blue line), "45rpm" (red line), 45 RPM (green line), and 45RPM (yellow line) for the same period :

and the case-insensitive graph: Ngram graph

And finally for "frames per second," here is the case-sensitive chart for "30 fps" (blue line), "30fps" (red line), 30 fps (green line), and 30 fps (no line—too few results) for the same period:

and then case-insensitive graph: Ngram graph

These charts show a consistent preference in published works for lowercase over all-caps treatment, and for open over closed presentation. But they also show that there has never been unanimity with regard to the proper treatment of such expressions.

I should note that Ngram reads and reports hyphenated forms (60-mph, 45-rpm, and 30-fps, for example) as open forms (60 mph, 45 rpm, an 30 fps)—but that doesn't skew the results in this case because the hyphenated forms occur primarily when the open form of the noun is being put to work as an adjective.

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    I wonder if they will still be using miles in 3005. :-) – Jim Aug 27 '16 at 21:09

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