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.
Thanks!
Best Answer
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.