# How to determine the alcohol content of a mixed-drink?

Title says it all: How do I determine the alcohol content of a mixed-drink (Cocktail, Longdrink)?

Note - I know the alcohol content of all ingredients.

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To a first approximation, you can just calculate the volume of pure ethanol in each of the alcoholic ingredients (total volume * %ABV = volume of pure ethanol), add those up, and divide by the total volume of all ingredients.

For example, a margarita with 35mL 40% ABV tequila, 20mL 40% ABV Cointreau, and 15mL lime juice would have alcohol content of (35mL*40% + 20mL*40% + 15mL*0%)/(35mL+20mL+15mL) = 31% ABV.

That's an approximation because the volumes are not strictly additive: mixing 50 ml pure ethanol with 50 ml water will actually give you something like 95 ml of the mixture. To get a truly accurate answer, you'll need to measure the volume of the final drink, and divide your total alcohol content by that.

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I'd say as long as this is for practical purposes (i.e. you're not trying to put the cocktail in a bottle with government-approved labeling) simple arithmetic is just fine. The approximation is way better than you imply, because the alcoholic ingredients are already mixtures, so a lot of the volume loss has already happened. Ice melting into the drink would be a far bigger effect. – Jefromi Nov 11 '12 at 15:30
I changed %ETOH to %ABV because that's how it's commonly referred to with alcoholic drinks, and went ahead and added an example, since it sounded like it might be the math the OP was wondering about. Please feel free to edit further if it's not to your liking. – Jefromi Nov 11 '12 at 15:34
Thanks guys, now I got it! It's just for my recipe collection in case guests ask if it's a strong drink - some drinks contain a lot of alcohol but taste like lemonade. – Sven Nov 11 '12 at 15:37
I was reading something last week, discussing ice in shaken cocktails -- there are some tricks to ensure that a lot of alcohol doesn't stay in the shaker attached to the ice. I don't remember if it was a link in a question on here, or something else that I stumbled across. – Joe Jun 6 at 15:23

If there are no significant other (non water, non alcohol) liquids involved (especially not heavy amounts of sugar), an areometer/spiritometer (available as a brewer's tool,\$10-\$20) should be able to tell you.

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