Traditionally, M is used as the symbol for thousands and MM for millions in the business world, particularly in accounting. However, there has been a growing tendency to use K as the symbol for thousands instead of M.

Would it be considered acceptable to use K for thousands and MM for millions, effectively mixing symbols?

For example, in a document that requires the use of symbols because of limited space in a table, I see "500K-1MM" to stand for "500,000-1,000,000". This document is written for a general professional audience.

My thoughts are:

If K and MM are used, it's bad style because the symbols are being mixed up. But if M and MM are used, non-experts might not even be aware that M is a symbol for thousands and get confused. It seems like that the safest choice to ensure comprehension is to use K and MM, but something about mixing the symbols just doesn't seem right to me.


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    I don't know that MM stands for "millions". In my universe, it's always just £1M for a million pounds. I wouldn't know what to make of £1MM. – FumbleFingers Jul 2 '14 at 20:44
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    I've been revising presentations for US financial-services CFOs and other senior managers for twenty years, and they have all used M for million, not thousand; I've never seen MM. Of course my guys rarely stoop to mentioning any value less than a hundred thousand ($0.1M) or so ... – StoneyB on hiatus Jul 2 '14 at 21:09
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    This would be a question of corporate jargon and not English, US or UK. – Oldcat Jul 2 '14 at 23:02
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    @WS2: I do have the vague sense that K and M aren't really part of the same set of abbreviations. I'm okay with K=Kilo, M=Mega, but it unravels slightly when I have to connect K=Kilo, M=Million. Partly for that very reason, I also used to sometimes use £000 on column headings. – FumbleFingers Jul 2 '14 at 23:19
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    For the purposes of clarity, you probably shouldn't mix SI prefixes with "business world accounting" symbols; Because there is overlap between these groups, there is a great possibility that confusion may result. I suggest you pick one convention of expression, and declare it near the beginning of any document. Incidentally, this doesn't really seem like an ELU question... – user867 Jul 3 '14 at 4:44

I worked in banking for 27 years (Federal Reserve Bank of Atlanta and Bank of America), and my experience in financial services was that M and MM were consistently used for thousands and millions, respectively. This practice was across the board - exam reports, internal reporting, and so on. They never used K for thousands.

It would be bad form to mix K and MM because they are two different systems of notation. The best path would be to determine what your audience is most likely to understand. M and MM are roman numerals where M is one thousand and MM is intended to denote "one thousand thousands." K comes from kilo which is the unit prefix in metric systems to indicate "times one thousand." The corresponding prefix for million is M.

So you should use either K and M or M and MM, but do not mix the two.

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    And probably establish at the start of your document or presentation exactly which convention you have adopted. – Andrew Leach Jul 3 '14 at 18:39
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    Thank you very much! This is exactly the kind of answer I was looking for! – Andrew Jul 17 '14 at 20:48
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    its not just finance, oil industry also (ab-)uses MM for millions, in terms like MMBO (1 million barrel of oil) and so on. – c69 Feb 8 '15 at 23:53
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    Roman numeral MM is for 2000 as XX is for 20. – corretge Apr 11 '17 at 7:45

In the general environment of municipal government, for dollars we use K for thousands, M for millions and B for billions.

However, I often see where those who are dealing with financing (banks and investment houses for bonds) use the MM for millions of dollars.

That being said, I think the most appropriate usage is using one alpha symbol consistently so that would lead to using K, M and B.

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  • B for billion? I have usually seen G (as in giga, another SI prefix) and T (tera) for trillion. – StenSoft Jun 12 '15 at 15:01
  • Some also use xxxxMM or xMMM for billion (1000^3), since billion may mean million million in some areas. See youtube.com/watch?v=C-52AI_ojyQ – Greg Bray Jan 27 '16 at 16:48

I have had the same dilemma and come to the conclusion that using k for thousands and MM for millions is a reasonable and pragmatic thing to do.

The problem with M is that depending on the audience it can mean either thousands or millions. This is ambiguous; hence, if you wish to be unambiguous the use of M to mean either thousands or millions is to be avoided. Thus, we're left with k and MM as to unambiguous ways to denote thousands and millions respectively.

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As one discovers from the many varient opinions this topic generates significant misunderstanding. By placing the first occurence of a given symbol (abbreviation) in each article or presentation within parenthises you remove all doubt about what you mean.

For example: "First quarter earnings were up by $2 Million (MM), a significant improvement over the the $250 Thousand (M) loss in the final quarter of last year.

Then you may use the abbreviations throughout your article without concern for being misunderstood.

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