Alcohol Units

Background

One UK unit is 10 ml (about 8 g) of pure alcohol. Units in a drink = volume in ml x ABV% divided by 1000. The unit system exists because drinks vary enormously in strength and serving size: a 25 ml measure of 40% spirit is one unit, but so is roughly half a pint of 4% beer, and a large 250 ml glass of 13% wine is more than three.

Interpreting the result

The UK Chief Medical Officers' low-risk drinking guideline is to drink no more than 14 units a week, for both men and women. If you regularly drink as much as 14 units, the advice is to spread it over three or more days rather than concentrating it, and to have several drink-free days. Fourteen units is about six pints of average-strength beer or ten small (125 ml) glasses of wine. The guideline describes a low-risk level, not a safe one: the CMOs are explicit that there is no level of regular drinking that carries no risk at all.

Advice

To keep health risks low, the UK guideline is no more than 14 units a week for both men and women, spread over three or more days, with some drink-free days. 14 units is about 6 pints of average beer or 10 small glasses of wine.

Worked example

A large glass of wine, 250 ml at 13% ABV: (250 x 13) / 1000 = 3.25 units. Three of those in an evening is 9.75 units — most of the weekly guideline in one sitting, and well into the range the guidance advises against concentrating.

Pearls / pitfalls

• Home measures are usually larger than pub measures — people routinely underestimate their intake because of pour size rather than number of drinks.
• Drink strengths have risen over time. A wine that would once have been 11% is now often 13-14%, so an old mental conversion undercounts.
• The advice for pregnancy is different: the safest approach is not to drink alcohol at all.
• Spreading intake matters independently of the total — the same weekly units concentrated into one or two sessions carries higher risk of both injury and liver harm.

Evidence & validation

The 14-unit weekly figure comes from the UK Chief Medical Officers' Low Risk Drinking Guidelines (2016), which for the first time set the same threshold for men and women and framed the advice in weekly rather than daily terms. The guidelines also advise against "saving up" units for a single occasion, and give separate advice for pregnancy, where the recommendation is not to drink at all.

Frequently asked questions

References

1. UK Chief Medical Officers. UK Chief Medical Officers' Low Risk Drinking Guidelines. 2016.

Related calculators