Alcohol Units and Standard Drinks Calculator

The formula

UK units = volume in litres × ABV percentage

It is that clean because of how a unit is defined. One UK unit is 10 ml of pure alcohol, which weighs about 8 g. A litre of 1% drink contains 10 ml of alcohol, so litres multiplied by percentage gives units directly.

A 750 ml bottle of 13% wine is 0.75 × 13 = 9.75 units. A pint of 5.2% lager is 0.568 × 5.2 = 2.95. A 25 ml single of 40% spirit is 0.025 × 40 = 1 unit exactly, which is where the whole system started.

Why the pour matters more than the drink

The phrase "a glass of wine" has stopped meaning anything useful.

A large 250 ml glass of 13% wine is 3.25 units. A small 125 ml glass of the same wine is 1.6. That is a factor of two, from the same bottle, described with the same words. Add the drift in wine strength, which has risen from around 11% to 13% or 14% over a few decades, and a glass poured today can carry twice the alcohol of one poured in the 1990s.

Home pours are the larger problem. Studies of self-poured drinks consistently find people pour substantially more than a measured serving, particularly into wide glasses, and consistently underestimate what they poured. Pouring a bottle into three glasses rather than the four many people assume is closer to what actually happens.

Units are not international

This trips people up constantly when reading health guidance from other countries.

• United Kingdom: 1 unit = 8 g of alcohol.
• Australia and much of Europe: 1 standard drink = 10 g.
• United States and Canada: 1 standard drink = 14 g.
• Japan: 1 unit = about 20 g.

So a US "two drinks a day" guideline is about 3.5 UK units a day, or 24.5 a week, which is well above the UK figure of 14. The countries are not disagreeing as much as the numbers suggest, but they are also not saying the same thing, and comparing the raw numbers without converting produces nonsense.

What the guidelines actually say

The 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 each week.

The spreading matters as much as the total. Fourteen units in one evening carries very different risks from fourteen units across a week: acute risks including injury and alcohol poisoning scale with the size of a session, while chronic risks including liver disease and several cancers scale more with the total.

Guidance in most countries has moved downward over the past decade. Canada's 2023 guidance was revised dramatically, from a previous weekly limit to advising that risk begins to increase above two standard drinks a week. The direction of travel has been consistent.

The health claims that did not survive scrutiny

For years the accepted position was that moderate drinking, particularly red wine, was protective for the heart. That claim has largely collapsed.

The main problem was the comparison group. Studies compared drinkers against non-drinkers, but non-drinkers include people who stopped because they were already ill, and people who never drank for reasons correlated with other health factors. That makes abstainers look unhealthier than they are and moderate drinkers look healthier.

Studies using Mendelian randomisation, which compares people by genetic variants affecting alcohol metabolism rather than by reported behaviour, and which is therefore much harder to confound, generally find no protective effect. The WHO position since 2023 is that no level of alcohol consumption is safe for health.

This does not mean a drink is dangerous. It means the risk curve starts at zero and rises, rather than dipping first, and the honest framing is that drinking is a trade you make knowingly rather than a health measure.

Calories, which nobody counts

Alcohol carries 7 calories per gram, closer to fat at 9 than to carbohydrate or protein at 4, and they arrive with no nutritional value at all.

A large glass of wine is roughly 200 calories. A pint of lager is around 220. Six pints over a weekend is about 1,300 calories, or most of a day's intake, and almost nobody includes it when tracking food.

Alcohol also suppresses fat oxidation while it is being metabolised, because the body prioritises clearing it, which is why the calories behave slightly worse than the number alone suggests.

Clearing it takes the time it takes

An average adult clears roughly one unit an hour, though this varies with body size, sex, food and liver function.

Ten units finishing at midnight means alcohol is still present well into the following morning, which is the mechanism behind most morning-after driving offences. Nothing accelerates it. Coffee, a cold shower, fresh air and exercise change how alert you feel while leaving your blood alcohol exactly where it was, which is a genuinely dangerous combination.