Mixing use of K for thousands and MM for millions

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.

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.

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 variant opinions this topic generates significant misunderstanding. By placing the first occurrence of a given symbol (abbreviation) in each article or presentation within parentheses 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.