Top definition
A formula to ensure you (or whoever you are buying beer for) gets the drunkest for lowest amount of money:

"Beer Score" = (Beer Size x Beer ABV) / Price

Used to get the score of the beer you are drinking and to compare against other beer's score.
Pint of Guinness costs \$5 at the bar... 16oz x 4.2 ABV / \$5 = 13

Quart of Olde English costs \$3 at the corner store... 32oz x 5.9 ABV / \$3 = 63

So using Beer Math it takes 5x as much money to get drunk off Guinness at the bar than it does from OE in parking lot.
by BSonBB December 29, 2012

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2
When alcohol is bought at the store for a group of people by one person and there is a dispute over how much change should be returned. The receipt is then presented and the group does the beer math to determine the correct change to be given back.
Josh: Dude, where is my change at?

Adam: There is none. I used all the money you gave me.

Josh: There is no way a case of beer cost 20 bucks.

Michael: Guess we have to get the receipt out and do the beer math.
by Denton is for Pimpin February 28, 2010

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3
A very rare form of math only used on a Friday and/or Saturday night when all of your friends who dont have a job want to party, sadly, without out the money to carry out such goals. It will only come into play when your plans are 'have a chill night with a twelve-pack with yourself or one other person' any other plans that you might have are exempt from ever having to use beer math.

HOW TO USE BEER MATH

One: you take the number of people that are going to show up adding possible no-shows or the classic 'unexpected's'.

Two: you roughly determine how much each person will have depending on serval factors, such as the time of day, the persons mood, the persons girlfriend (whether or she approves of drinking) the night before, (whether or not a possible hangover is still very much effective) so on and so forth.

Three: you then compare that to the number of beers you have total assuming of course you have no money to buy more. By calculating this equation you can then figure out roughly how many beers you will ultimately have drank by the end of the night.

Example;

~6 people
two will only drink 2-3
the rest will have 6 or more

Divided into 30 beers

= a shitty Friday night.
What!??! Alex and Share are comming too??!? *mumbles to himself while counting fingers* Shit! Using Beer Math that only leaves me with five beers!!
by The Drinkerr July 20, 2010

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4
Commonly used to figure out how many beers or wine coolers have been drank by your friends at a social gathering.

(it's almost never correct)
Party host: "Whoa! the whole 24 pack is gone! how much have you guys drank?"

Guy 1: "Well I drank 6"

Guy 2: "I only had 5"

Party host: "and I had 5, so who drank the last beer?"

Guy 1: "Not me"

Guy 2: "Not me"

Party host: "Fucking beer math!!"

The Urban Dictionary Mug

One side has the word, one side has the definition. Microwave and dishwasher safe. Lotsa space for your liquids.