Alcohol unit calculator
Units from the strength and the size. A unit is ten millilitres of pure ethanol, so a large glass of wine is three and a quarter of them. Nothing you type here leaves your browser — it is worked out on your own device, so there is nothing to send and nothing to log.
This is arithmetic, not medical advice. The 14-unit figure is guidance from the UK Chief Medical Officers dated 2016, not a fact about alcohol. If you have been drinking, do not drive — nothing on a web page can tell you when it is safe to.
A glass of wine is not a unit, and never was
A unit is ten millilitres of pure ethanol. That is the entire definition, and the formula on every NHS page — ABV% × ml ÷ 1,000 — is the same statement written out.
So a large 250 ml glass of 13% wine is 3.25 units, which is a quarter of the week's guideline in one glass. A pint of 5.2% lager is 2.95 units, so four pints is the week. The only drink that is actually one unit is a single 25 ml measure of 40% spirit — which is where the scale came from.
14 units is a recommendation, with a date on it
The UK Chief Medical Officers advise no more than 14 units a week on a regular basis, for men and women alike. That figure dates from 2016; before then the advice was 21 for men and 14 for women, and the guidance also asks that the 14 be spread over three or more days rather than taken at once.
It is guidance from a named body on a particular date, not a fact about alcohol. These figures were checked against the NHS on 21 September 2026.
A “standard drink” is not a unit
The UK unit is British and almost nowhere else uses it. The American standard drink is 14 grams of pure ethanol, which is 1.77 UK units. So American advice of “no more than 14 drinks a week” would be about 25 UK units — nearly double the British guideline, for the same number.
Australia's standard drink is 10 grams, which is 1.27 UK units. Nobody has agreed on any of this.
How long it takes to clear, and why not to rely on it
The rule of thumb is about one unit an hour, and it is a very rough thumb. The real rate depends on body size, sex, liver function, whether you have eaten and what else is in your system, and it varies between people by a factor of two. Coffee, cold showers and fresh air do nothing at all except make you a more alert drunk.
If you have been drinking, do not drive. The morning after a heavy night is the case people get wrong, and this page will not tell you it is safe, because it cannot know.
Drinks got stronger while glasses got bigger
A “glass of wine” in 1980 was 125 ml of about 11% wine — 1.4 units. A large glass today is 250 ml of 13% — 3.25. The word did not change and the quantity more than doubled. The same has happened to beer: 3.5% was ordinary and 5% now is.
What it will not do
- It will not estimate your blood alcohol level. That needs body mass, sex, time and food, and the answer would still be too uncertain to act on.
- It will not tell you whether you are fit to drive. Nothing on a web page can.
- It will not know what was actually poured. Home measures are famously generous and an ABV figure on a label is allowed a tolerance.