The amount of alcohol in your drink is determined by the concentration of alcohol in the product you choose and the size of your drink.
Drink strength. Drinks vary considerably in their alcohol concentration or strength. Different countries measure alcohol strength in different ways.
In most places, the concentration is measured as the percentage of pure alcohol in the product by its volume. This measure is called alcohol by volume, or ABV. In some countries, this percentage is also called “degrees” of alcohol.
In other countries, concentration is measured in a unit called “proof,” which is simply double the ABV. For example, a drink that is 40% alcohol by volume would be labeled “80 proof.”
Alcohol strength can also be measured by weight. The percentage of alcohol by weight is a bit less than the percentage of alcohol by volume because alcohol weighs less than water.
Serving size matters! Drink serving sizes differ widely by the local custom, occasion, glass size, and even depends on who does the pouring. Unless you are drinking from a pre-packaged bottle or can, or in a location where pouring size is regulated by law, you need to know your glass size and understand your pour.
So, how do I know how much alcohol is in my drink? To answer this question, you need to know both the ABV and the size of your drink.
Typically, beers are about 4 to 5% ABV, wines about 12 to 14% ABV, and distilled spirits about 40% ABV. But these figures may not be accurate for your drink. Different styles of drinks have very wide variation in alcohol content. To know how much alcohol is in your drink, start with learning the actual ABV. Often, the ABV is clearly marked on the package, is available on company websites, or you can ask your bartender or server.
Because of the differences in strength, lower ABV drinks are often served in larger sizes than higher ABV drinks. For example, servings of beer are sometimes bigger than servings of wine, and distilled spirits are served in even smaller sizes and often mixed with other liquids.
To calculate how much alcohol is in your drink, multiply the ABV by size of the drink, and the result is the volume of pure alcohol in your drink.
In some countries, there is an official “standard” size for drinks. This standard is often used to:
- Allow servers in bars and restaurants to measure how much they are serving;
- Allow customers to know what they are being served; and
- Give advice to people on how much they are drinking and what the potential effects are likely to be on their health.
In many countries, 10g of ethanol is considered to be a drink or unit. However, in the United States, for instance, a standard drink contains 14g of ethanol, while a U.K. standard unit contains 8g of ethanol.