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K as an Abbreviation for Thousands

Date: 05/29/2002 at 21:48:38
From: Caryll 
Subject: Representation of thousands and millions

In class last night my professor wrote $30M and intended it to 
mean thirty thousand dollars.  I was taught that 30K meant thirty 
thousand.  I looked at several of the sites referencing Roman 
numerals, but can't find anything about 'K'.  Can you assist?

Date: 05/29/2002 at 22:47:10
From: Doctor Peterson
Subject: Re: Representation of thousands and millions

Hi, Caryll.

When we write "30 K" for 30,000, we are not using Roman numerals 
but pseudo-metric, where K stands for "kilo-".

For the same reason, "30 M" means 30,000,000, using M for "mega-" 
(or just "million").

It would be wrong to use Roman numerals this way; M here can't 
stand for thousand. But I suspect it's a common mistake.

See this site, listed in our FAQ, that tells all there is to know 
about units:

    How Many?

    an informal abbreviation for one thousand used in
    expressions where the unit is understood, such as "10K
    run" (10 kilometers) or "700K disk" (700 kilobytes or
    kibibytes). Note that "K" is also the symbol for the
    kelvin (see below). Also note that the symbol for the
    metric prefix kilo- (1000) is actually k-, not K-. 

    M [1] 
    informal abbreviation for million in expressions where
    the base unit is understood, as in "500M hard drive"
    (500 megabytes or mebibytes). In chemistry, M is the
    symbol for "molar" (see below). 

    M [2] 
    the Roman numeral 1000, sometimes used in symbols to
    indicate a thousand, as in Mcf, a traditional symbol
    for 1000 cubic feet. Given the widespread use of M to
    mean one million, this older use of M to mean 1000 is
    very confusing and should be scrapped. 

See also

   Is K a Roman numeral?

- Doctor Peterson, The Math Forum 

Date: 05/30/2002 at 08:04:43
From: Caryll 
Subject: Thank you (Representation of thousands and millions)

Many thanks for the clarification.  Keep up the good work.

Date: 10/08/2002 at 15:25:33
From: Chris Chang
Subject: On M representing Thousands

I believe it is incorrect for you to state that usage of M, 
such as $10M, is wrong to represent thousands.  

While $10K is more common, there has certainly been a 
convention for many years in various businesses for 
$10M to mean $10,000 and for $10MM to mean $10,000,000.

This is a confusing issue because to my knowledge there
is no definitive standard. Instead, convention has varied
by field, and case to case. Indeed I am sure there are
different people right now using M to mean thousands
while others are using it to mean millions.

I suggest checking the convention in a specific situation.  

Chris Chang

Date: 10/08/2002 at 15:35:04
From: Doctor Peterson
Subject: Re: On M representing Thousands

Hi, Chris.

Can you give  me any references to show this usage, either a manual 
of some sort, or an example (preferably on the Web so I can see it 
easily)? I will still stand by my statement that it is "wrong," 
because as you admit it is very confusing; but as we know many things 
that are wrong are nevertheless standard, and it would be good to 
point that out in case people confuse the two concepts. 

Also, note that I referred to Russ Rowlett's page, where he says that 
M for thousand IS used, but should be eliminated, which is what I am 
saying too. Neither of us claims that it is only used mistakenly, 
just that it is not a good idea.

The references I found some from government and industry, often in 
energy or forest related fields where Rowlett's "Mcf" is also found:

  Glossary - Southern Appalachian Forest Coalition

    M - thousand 
    M$ - thousands of dollars 
    MAUM - thousand animal unit month 
    MBF - thousand board feet 
    MCF - thousand cubic feet 
    MM - million 
    MM$ - millions of dollars 
    MMBF - million board feet 
    MMCF - million cubic feet 
    MMRVD - million recreation visitor-day 

  Energy INFOcard

    MMbd = million barrels per day; Mcf = thousand cubic feet
    tcf = trillion cubic feet; kWh = kilowatthour; MM = million 

  Fuel Alcohol Plant Cost Study Cases


    $25 MM

The frequent coexistence of MM in money and in unit names suggests 
that in fields where such obsolescent units are used, the habit 
carries over into financial notation.

I can also refer to these entries in Rowlett that I had missed; they 
confirm my impression of the industries affected:

    an abbreviation for one million, seen in a few traditional
    units such as those listed below. The abbreviation is meant
    to indicate one thousand thousand, M being the Roman numeral
    1000. However, MM actually means 2000, not one million, in
    Roman numeration. 
    MMb, MMbo 
    symbols for one million barrels of oil; see megabarrel above.
    MMBF or MMBM 
    symbols sometimes used in U.S. forestry for one million board
    feet. One MMBF represents a volume of 83 333 cubic feet or
    2360 cubic meters. "BM" stands for "board measure." 

    MM Btu 
    traditional symbol for one million Btu (about 1.055 057
    gigajoules (GJ)), a unit used widely in the energy industry.
    This unit is also called the dekatherm. 

    a symbol for one million cubic feet (28 316.85 m3, or 
    28.316 85 megaliters). 

    MM scfd 
    symbol for one million standard cubic feet per day, the
    customary unit for measuring the production and flow of
    natural gas. "Standard" means that the measurement is
    adjusted to standard temperature (60 F or 15.6 C) and
    pressure (1 atmosphere). 

As much as I dislike this notation, I certainly have to admit that 
it is still current in some fields, and has to be lived with for 
now. The professor in the original question has the final say.

Thanks for pointing out this interesting backwater of notation!

- Doctor Peterson, The Math Forum

Date: 10/08/2002 at 16:38:52
From: Chris Chang
Subject: On M representing Thousands

I agree with you that it would be nice to get rid of MM representing 
millions and simply use M, or any sort of standardization so we know 
what people mean!

I was specifically thinking of the financial industry, which your 
Rowlett citation mentions, where MM is still in regular use.  
Admittedly, now that I look around and think about it, I have not 
seen M used much recently - primarily because figures tend to be 
larger and so are not often quoted in thousands.

A few references follow:

Done Deals Definitions
A site that uses M for thousands and MM for millions.

Merrill Lynch glossary
Merrill Lynch glossary.
See Market Cap entry, uses $MM for millions of dollars.
Median Market Cap uses $M for thousands of dollars, although
definition of $M is not stated explicitly.

Information or Babel? - Madnick
section 2.1 paragraph 3:
(as an aside, even if given a clue, such as 23M, there may be a 
problem because sometimes M means millions, sometimes it means 
thousands - in which case MM is used to mean millions)
Exactly the various usage we are talking about.

7-11 Financial Report
This financial report just uses MM for millions.

Yale Career Information Center
This Yale guide uses K for thousands, M to mean one million, and MM 
to represent millions.  This seems even more confusing to me, but 
goes to my point that there is a lot of different usage around.


Date: 01/17/2003 at 18:16:31
From: Richard Wilkes
Subject: Recent article on the letter M

I noted with agreement your statement that "K" refers to thousands, 
"M" to millions. However, it is not uncommon in the business world to 
see "M" for thousands, "MM" for millions, and "MMM" for billions.  
This probably is a fairly recent trend/shortcut in finance. The same 
holds true for dashes, such as one the length of a hyphen, used as a 
superscript above and right of the number (as one would in noting that 
a number has been squared or cubed, for example). I have seen (and 
have used myself when writing down numbers) one (superscript) dash for 
thousands, two for millions, three for billions, and so on.

Richard Wilkes
Financial/M&A Advisor
Houston, TX

Date: 10/01/2005 at 18:22:29
From: George
Subject: K as an Abbreviation for Thousands

You mention a preference for the use of "K" rather than "M" for 
thousands.  I have been in and around the printing industry for over 
twenty five years.  In our industry, it is true that K is the 
standard used to indicate thousands in some parts of the world, and 
M is the standard used in others, including the United States.  Until 
a consensus is reached, I agree that it could be confusing; however, 
until that time, there is an easy way to avoid that confusion. Don't 
focus on changing the symbol for thousands, which would be both 
difficult and time consuming, considering the various cultural 
predispositions.  Instead, always use MM for millions.  That way neither
K nor M would be mistaken for millions in my industry as well as 
many others.

Date: 10/01/2005 at 21:15:12
From: Doctor Peterson
Subject: Re: K as an Abbreviation for Thousands

Hi, George.

That's not a bad thought; though if you use M for thousands, that
could still be mistaken for millions until the reader notices that you
are using MM for that purpose. If you go further and use only K and
MM, you could avoid ambiguity entirely (as long as your audience is
not so stuck on one tradition that they don't recognize the other). On
the other hand, your rule just takes two individually logical systems
and combines them into a hybrid that makes no sense, and that would
have to be replaced eventually anyway if we want to migrate to a
single consistent system. I don't quite like it, but could probably
live with it if I had to!

I think there will always be some confusion, but your idea is a
possibility for reducing it.

- Doctor Peterson, The Math Forum
Associated Topics:
Middle School Definitions
Middle School History/Biography
Middle School Number Sense/About Numbers

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