Alcohol Units Calculator

How units are calculated

A UK unit is 10 millilitres, or 8 grams, of pure alcohol. Units equal volume in millilitres times alcohol by volume percentage, divided by 1,000.

A 175 millilitre glass of 13% wine is 2.3 units. A pint of 5% lager is 2.8. A 25 millilitre measure of 40% spirit is 1.

Other countries use different standard drink definitions, which makes international comparison of guidelines confusing. A US standard drink contains 14 grams of alcohol, nearly two UK units, and Australian standard drinks are 10 grams.

The guidelines

UK Chief Medical Officers advise no more than 14 units a week for both men and women, spread over three or more days, with several drink-free days.

The guidance was revised downward in 2016, and the accompanying report was explicit that there is no completely safe level of drinking, and that the guideline represents a low-risk level rather than a safe one.

Fourteen units is six pints of average-strength beer or about a bottle and a half of wine. That is considerably less than many people assume the guideline permits.

Why home measures understate

Almost everyone pours more than a standard measure at home. A generous glass of wine can be 250 millilitres, which at 14% is 3.5 units against the 2.3 of a 175 millilitre glass.

Alcohol content has also risen. Wine that was commonly 11% or 12% is now frequently 13% or 14%, and craft beers regularly exceed 6%, so the same volume carries more alcohol than the mental model formed years ago.

Which means self-reported intake systematically understates actual intake, and the gap is largest for people drinking at home. Measuring pours for a week is usually a surprise.

How the body processes it

The liver metabolises roughly one unit per hour, with substantial individual variation by body size, sex, genetics and liver health.

That rate is fixed and cannot be accelerated. Coffee, cold showers, food and exercise do not speed elimination; they may increase alertness, which is different from being sober and is more dangerous for exactly that reason.

The practical implication for driving is that alcohol consumed at night is often still present in the morning. Eight units finishing at midnight takes roughly eight hours to clear, which puts a driver over the limit at eight in the morning.

The risks, stated proportionately

Alcohol is causally associated with seven types of cancer, including breast and bowel, and the association begins at low levels of consumption rather than at a threshold.

Liver disease, cardiovascular effects, dependence and mental health effects all scale with intake. The apparent protective effect of moderate drinking on heart disease that appeared in older observational studies has been substantially undermined by better-designed research, particularly Mendelian randomisation studies.

Anyone concerned about their drinking, or who finds it difficult to reduce, should speak to a GP. Alcohol withdrawal in dependent drinkers can be medically dangerous and occasionally fatal, which is why stopping abruptly without advice is not recommended for anyone drinking heavily.

Tracking units accurately for a fortnight is a more informative exercise than it sounds, because most people are surprised. The gap between estimated and actual intake is largest for wine at home and for rounds bought in company, both of which are poured or bought without measuring. Recording each drink at the time, rather than reconstructing the week on Sunday, removes most of the error, and the resulting figure is the one worth comparing against the guideline rather than the one memory supplies.