What is the Proof of My Cocktail?

Calculating the Alcohol Content of Mixed Drinks

Whiskey is carefully tested for quality and alcohol volume prior to bottling.
It is time to geek out on cocktails and use math to estimate how strong our drinks really are. Monty Rakusen/Cultura/Getty Images

It is easy to tell how strong a liquor is. We just read the bottle's label and look for its proof or ABV. Have you ever wondered what the proof of your cocktail is?

Things can get a little complicated when we start combining different liquors with non-alcoholic mixers, shaking it with ice and adding water, and everything else that we do to create great drinks. Unless you are willing to carry a testing kit filled with scientific gadgets to the bar, there is no straight answer as to how strong the drink in front of you really is.

There is, however, a simple formula that will show us how to estimate the strength of our drinks and we can decrease or increase their potency if we know a few basic facts.

Measuring the Strength of Liquor

There are two numbers on every liquor bottle that tell us exactly how strong the distilled spirit is: alcohol by volume (ABV) and proof. The two can easily be converted back and forth, though they have different purposes.

What is ABV? Alcohol by volume (often read as alc/vol or ABV on the label) is the percentage of alcohol content to the total volume of liquid inside the bottle.

During the distillation process, the distiller will produce a very strong distillate that comes directly out of the still. This is then watered down to the bottling strength, or the alcohol by volume indicated on the label.

This is required on every liquor, wine, and beer bottle sold on the legal market.

What is Proof? The proof is a number that is primarily used in the United States to denote the taxes a distiller needs to pay on a certain amount of liquor.

Drinkers tend to use proof to describe the potency of liquor as well. It is easier than saying alcohol by volume or alcohol content (both of which make you sound uncool)Beer and wine do not use proof on the label.

The Average ABV of Alcoholic Beverages

Most alcoholic beverages fall into a certain ABV range:

If you did some quick math while reading through this list, you noticed the easy formula that allows us to switch between ABV and Proof:

ABV x 2 = Proof

For example:

  • 40% ABV is 80 proof
  • 15% ABV is 30 proof

Calculating the Alcohol Content of a Cocktail

This is where we begin to get our cocktail geek on because most drinkers only care that they can taste the alcohol. While many people could care less about finding out what the proven strength of their drink is, some of us enjoy a little trivia (even a little math) and this is for us.

It's only an estimate. These calculations can only be an estimate because of a few factors and one of the biggest unknowns in our formula is how the drink is mixed.

Every bartender mixes ​a drink a little differently.

The size of the glass, particularly when building drinks, is also going to play a role in the drink's strength. If you are using a 7-ounce collins glass you will have a stronger drink than if you filled 10-ounce highball glass with soda.

The Cocktail Proof Formula

The general formula that we can use to estimate the strength of a cocktail is:

(Alcohol Content x Liquor Volume / Total Drink Volume) x 100 = % Alcohol by Volume

We will begin with the classic Martini recipe as an example:

2.5 oz gin - 40% (.40) ABV or 80 proof
.5 oz dry vermouth - 15% (.15) ABV or 30 proof
.5 oz melted ice - (always factor in dilution)
( .40 x 2.5 ) + ( .15 x .5 ) = 1.0752.5 + .5 + .5 = 3.5 oz
(alcohol content x liquor volume)(total drink volume)
1.075 / 3.5 = .30 x 100  = 30% ABV or 60 proof

At 60 proof, the Martini is a very strong drink. This is understandable because it is made of only gin and vermouth. The ice brings it down just slightly below the gin's bottling proof, so the average Martini is almost as strong as a shot of tequila. Of course, this will vary if you prefer less gin and more vermouth in your Martini.

Next, we will look at a simple highball drink, the Tom Collins:

1.5 oz gin - 40% (.40) ABV or 80 proof
1 oz lemon juice 
.5 oz simple syrup 
4 oz club soda 
.5 oz melted ice 
( .40 x 1.5 ) = .601.5 + 1 + .5 ++ .5 = 7.5 oz
(alcohol content x liquor volume)(total drink volume)
.60 / 7.5 = .08 x 100  = 8% ABV or 16 proof

As you can see, in a taller drink where more volume is taken up by non-alcoholic mixers, the strength is significantly lower. In fact, it is only slightly stronger than a glass of wine.

Alcohol Content and Liqueurs

While we can generally assume that gin, vodka, whiskey, and other base spirits are 80 proof (and the bottle will clearly state if it's 100 or above), liqueurs are not so easy. Different liqueurs will have a different alcohol content.

The vast range of orange liqueurs is a perfect example:

  • Triple sec tends to be less than 30% ABV (60 proof).
  • Grand Marnier and Cointreau are both bottled at 40% ABV (80 proof).

Both of these top-shelf liqueurs have the same alcohol content as most of the rums and tequilas that they are mixed with.

Even two different brands of the same liqueur may have different alcohol contents.

Let's break triple sec down even further:

  • Arrow Triple Sec is 17% ABV (34 proof).
  • Bols Triple Sec is 21% ABV (42 proof).

If alcohol content is a concern for you, then it is very important to read the bottle. Though at times (such as in this particular brand comparison) you may also be sacrificing quality.

Online Calculator

If you would like to know the proof of a particular cocktail without doing the math yourself, you can use an online tool like the Cocktail Content Calculator on the National Institutes of Health Rethinking Drinking website.

This is a very handy tool that will estimate the alcohol content of a certain recipe. It is only a generalized tool and should not be used to test the true proof of any drink because, as mentioned above, there are many factors that affect the final strength of any mixed drink.