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. You simply need to read the bottle's label and look for its proof or alcohol by volume (ABV). This will tell you whether the whiskey or vodka you're pouring is the standard 80 proof, or a little higher or lower. Yet, have you ever wondered what the proof of your cocktail is?

Things can get 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 can help you estimate the alcohol content of your mixed drinks. It can also help you decrease or increase a drink's potency if you know a few basic facts.

Measuring the ABV 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 reads as alc/vol or ABV on the label. It is given as a percentage and measures the amount of alcohol that is in a bottle compared to the total volume of liquid.

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.

ABV is required on every alcoholic beverage sold on the legal market, including all liquor, wine, and beer.

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.

American 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 can make you sound uncool)

Proof is only used on distilled spirits; you will not find the word on beer and wine labels.

The Average ABV of Alcoholic Beverages

The alcohol content for most alcoholic beverages falls into a certain range:

  • Brandy, gin, rum, tequila, vodka, and whiskies are typically 40 percent ABV or 80 proof. Some high-proof liquors—primarily whiskies and rums—reach over 50 percent ABV (100 proof). You will also notice that many flavored vodkas and similar liquors are bottled at 35 percent ABV (75 proof).
  • Liqueurs tend to range from 15 to 30 percent ABV or 30 to 60 proof. Some, such as Cointreau however, are also 40 percent ABV (80 proof).
  • Beers can range from 3 to 13 percent ABV.
  • Wines tend to range from 8 to 14 percent ABV.

If you did some quick math, you noticed the easy formula that allows us to switch between ABV and proof:

ABV x 2 = Proof

For example:

  • 40 percent ABV is 80 proof
  • 15 percent 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 of a drink's strength because of a few factors. One of the biggest unknowns in our formula is how the drink is mixed.

Every professional and home bartender mixes ​drinks 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, for instance, you will have a stronger drink than if you make the same drink in a 10-ounce highball glass and fill it with soda.

It's a simple matter of diluting down the alcohol with a non-alcoholic ingredient.

The Cocktail Proof Formula

While we cannot know the exact alcohol content of mixed drinks, there is a basic formula that we can use to estimate any drink's strength:

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

It's a bit confusing at first, but once you get the hang of it, it's relatively simple. We will begin with the classic martini recipe as an example.

A Martini's Stronger Than You Think

You begin by breaking down each of the alcoholic ingredients, multiplying the volume of each by their individual strength. You must also factor in dilution because this adds to the drink's total volume.

Ingredient VolumeStandard ABV
2.5 oz gin - 40% (.40) ABV or 80 proof
.5 oz dry vermouth - 15% (.15) ABV or 30 proof
.5 oz melted ice - standard dilution allowance

With that information, you will then add up the total alcohol content per liquor volume. You will also need to add up the drink's total volume. 

( .40 x 2.5 ) + ( .15 x .5 ) = 1.0752.5 + .5 + .5 = 3.5 oz
(alcohol content x liquor volume)(total drink volume)

These two numbers are then plugged into our proof formula.

1.075 / 3.5 = .30 x 100  = 30% ABV or 60 proof

The result is that the average gin martini is 30 percent ABV, or 60 proof. That is a very strong drink and 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. Of course, this will vary if you prefer less gin and more vermouth in your martini.

And yet, this is a good reminder that the average martini is almost as strong as a shot of tequila. You will find that similar all-alcohol "up" drinks like the Manhattan and rusty nail are just as strong.

Tall Drinks Are Lighter

Not all of the drinks we mix in the bar are that strong, though. Many of our favorite happy hour and casual sipping drinks include juices, sodas, and other non-alcoholic mixers. These ingredients significantly reduce the impact of the alcohol.

We will use a simple highball drink, the Tom Collins, for our example here. Notice how gin is the only liquor, so it is the only ingredient that we need to worry about for the initial alcohol content calculation. The other ingredients are simply factored into the drink's total volume.

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)

Just like the martini, all that needs to be done is to plug these two numbers into the cocktail proof formula:

.60 / 7.5 = .08 x 100  = 8% ABV or 16 proof

As you can see, in a taller drink with a volume taken up primarily by non-alcoholic mixers, the strength is significantly lower. In fact, at 8 percent ABV (16 proof), the average Tom Collins is equivalent to a glass of wine. That is why you will not get as drunk when enjoying a few rounds of these taller drinks as you would after a few martinis.

Alcohol Content and Liqueurs

Liqueurs are the great variable in this equation. 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. They will vary from one brand to another, even between liqueurs of the same style or flavor.

The vast range of orange liqueurs is a perfect example:

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

Both of these top-shelf liqueurs have the same alcohol content as most of the rums and tequilas that they are often mixed with. Therefore, a margarita made with Cointreau will naturally be stronger than one made with the average triple sec.

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 percent ABV (34 proof).
  • Bols Triple Sec is 21 percent ABV (42 proof).

If alcohol content is a concern for you, then you will want to pay attention to the bottle's label. Though, at times (such as in this particular brand comparison), you may also be sacrificing quality by going with the lower-proof option.

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. The Cocktail Content Calculator on the National Institutes of Health Rethinking Drinking website is a good one.

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 we learned, there are many factors that affect the final strength of any mixed drink.