Alcohol Units Calculator

A 'unit' of alcohol is a standardised measure used in the United Kingdom to quantify the amount of pure ethanol in a drink. One unit equals 10 mL (or approximately 8 grams) of pure ethanol. The unit system was introduced to make it easier for people to compare different types of alcoholic drinks — a pint of strong lager, a large glass of wine, and a double spirit can all be expressed in the same currency of units, removing the confusion of comparing percentages across very different drink sizes.

The formula is straightforward: multiply the drink's volume in millilitres by its ABV percentage, then divide by 1000. For example, a 330 mL bottle of beer at 5% ABV contains (330 × 5) ÷ 1000 = 1.65 units. This formula works for any alcoholic drink regardless of type. The ABV percentage is always printed on the label and represents the proportion of the liquid that is pure ethanol by volume. Dividing by 1000 scales the result correctly because 1 unit = 10 mL ethanol, and (volume × ABV%) gives ethanol in mL × 10, so dividing by 1000 yields units directly.

This calculator goes further by computing total units across multiple drinks, the mass of pure ethanol consumed in grams (using ethanol's density of approximately 0.789 g/mL, rounded to 8 g per unit for the standard UK definition), and the percentage of the UK's recommended weekly low-risk limit of 14 units. The 14-unit guideline applies equally to men and women following the 2016 update to the UK Chief Medical Officers' low-risk drinking guidelines. Spreading consumption across three or more days is also recommended rather than consuming all units in one or two sessions.

This calculator uses the standard UK definition of one unit (10 mL pure ethanol) and the UK CMO weekly guideline of 14 units. Other countries use different standard drink definitions: in the USA, one standard drink contains approximately 14 g (17.7 mL) of pure ethanol; in Australia, one standard drink is 10 g (12.7 mL). Always check which national standard applies to you. The weekly limit percentage shown here is therefore only directly applicable to UK guidelines.

ABV values on labels are nominal and can vary slightly batch to batch — particularly in craft beers, cask ales, and home-produced drinks. Wine ABV can range significantly from what is printed on older or natural wine labels. The formula assumes all listed ABV is accurate. Additionally, this calculator provides informational output only and does not account for individual factors such as body weight, sex, liver function, medications, or tolerance, all of which influence how alcohol affects a specific person. It is not a substitute for medical advice. If you are pregnant, on medication, or managing a health condition, consult your GP regarding safe alcohol consumption.