What is a unit of alcohol?

Units

A unit of alcohol is the percentage of alcohol in a given volume of an alcoholic beverage. This is a standardised way to compare alcohol content in alcoholic beverages, applying across drink types and sometimes differing by region. This allows a user to get an accurate and comparable representation of the amount of alcohol they drink. For example, there is a different number of units of alcohol in a bottle of beer compared to a glass of wine, although they both count as one drink.

In South Africa, a unit of alcohol is accepted as the percentage of pure alcohol per 10 ml of a beverage. Sipped takes the average of the percentage of alcohol within that alcohol category. For example, beer usually has around 4 - 5% alcohol per 10 ml and wine usually has 14%. A shot of tequila, a single whiskey or a single vodka usually have around 40% alcohol per shot or single serving, however, you usually consume a smaller amount of vodka (i.e a single vodka is 25 ml) as opposed to beer in a beer bottle (i.e 330 ml).

Sipped accounts for differences in volume and alcohol content by taking the volume of the drink and multiplying it by the alcohol content per 10 ml. For example, a bottle of beer is 330 ml and has around 4.5% of alcohol per 10 ml of that volume. Therefore, we take the volume of the drink, 330 ml, and divide that by 10 to get the number of 10 ml units and then multiply that by the percentage of alcohol in each of those units, 4.5%, to reach 1.485 as the number of units of alcohol consumed when logging a beer. 

Common Drink Units

Using the above explanation we can calutlate the units of alcohol in common drinks

Beer

A bottle of beer = 330 x 4.5% / 10
= 1.485 units

man holding a beer on a beach

Glass of Wine

A glass of 175 ml wine = 175 x 14% / 10
= 2.45 units

lady holding a glass of red wine while reading a book
a cocktail with a lime on the rim

Single Vodka

A single Vodka  = 25 x 40% / 10
= 1 unit

a shot of tequila, a lemon and a salt shaker

Tequila 

A shot of tequila  = 25 x 40% / 10
= 1 unit

We can, therefore, see that even a double vodka has fewer units of alcohol than a glass of wine. We don’t usually think of units of alcohol this way, as we think vodka has a higher alcohol percentage, therefore, must be higher in units. Although we don’t naturally think in units, it’s useful to record alcohol consumption in units because they are comparable across beverage types and more accurately represent alcohol consumption.

The trick here is how much volume of that alcohol we consume.