About alcohol units
An alcohol unit is a simple way to express how much pure alcohol a drink contains, so that drinks of different sizes and strengths can be compared on the same scale. In the UK, one unit is defined as 10 mL (about 8 grams) of pure alcohol — the amount an average adult body processes in roughly one hour. This calculator converts any drink into units from just two numbers: how much liquid is in the glass, and how strong it is.
The formula
Units are found by multiplying the volume of the drink in millilitres by its strength (ABV, alcohol by volume, as a percentage) and dividing by 1000:
- Units per drink = ABV(%) × volume (mL) / 1000. A 175 mL glass of 13% wine is 13 × 175 / 1000 = 2.3 units.
- Total units = units per drink × number of drinks. Three of those glasses is about 6.8 units.
- Grams of pure alcohol = units × 8, because one unit is 8 g of ethanol (10 mL at a density of about 0.789 g/mL).
The ABV figure is printed on almost every bottle or can, and the serving volume is either the container size or your pour. That is all the information the formula needs.
Putting the result in context
The UK Chief Medical Officers advise not regularly drinking more than 14 units a week, for both men and women, ideally spread over three or more days rather than concentrated into one session. The calculator shows what percentage of that 14-unit weekly guideline your entered drinks represent, so a single evening can be weighed against a whole week's guideline.
When to consult a professional
This tool performs a units conversion only; it does not estimate blood alcohol concentration, intoxication, or fitness to drive, all of which depend on body weight, sex, food, time, and metabolism. If you are concerned about your drinking or its effect on your health, speak with a licensed healthcare provider.