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.

  • 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.


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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