🍺 Alcohol Units Calculator: UK Units and US Standard Drinks

What is the Alcohol Units Calculator?

Alcohol is measured by the amount of pure ethanol a drink contains, not by how much liquid is in the glass. A large glass of strong wine can hold more pure alcohol than a pint of ordinary beer, even though the beer looks like the bigger drink. To compare drinks fairly, health bodies use a fixed amount of pure alcohol as the yardstick. The UK uses the unit, where one unit is 10 ml (about 8 g) of pure alcohol. The United States uses the standard drink, defined as 14 g (about 0.6 fl oz) of pure alcohol. The two systems describe the same thing on different scales, which is why a single drink can read as several UK units but only one or two US standard drinks.

The UK unit formula is simple: units = volume in millilitres x ABV percent divided by 1000. A pint of 5% beer is 568 x 5 divided by 1000, which is 2.8 units. The grams of pure alcohol come from multiplying the volume by the ABV as a fraction and then by the density of ethanol, which is 0.789 g per ml: grams = ml x (ABV divided by 100) x 0.789. Dividing those grams by 14 gives the US standard drinks. Because the formulas only need volume and ABV, you can work out any drink, including home pours and cocktails, as long as you know roughly how strong it is.

ABV (alcohol by volume) is the single most important number on the label, and it has crept upward over the years. Many craft beers are now 6% to 8% rather than the old 4%, and a typical wine sits around 13% to 14% rather than 11%. A bigger glass at a higher strength means a drink that used to be one unit can now be three. The US guide of roughly one standard drink being a 12 oz (355 ml) beer at 5%, a 5 oz (148 ml) glass of wine at 12%, or a 1.5 oz (44 ml) shot of 40% spirits only holds when the strength matches those assumptions, so a strong craft beer or a generous home pour can quietly be two drinks.

Different countries set the reference amount differently, so the same drink can read as a different number depending on where you are. The UK uses 10 ml (8 g) per unit, the US uses 14 g per standard drink, Australia and most WHO guidance use 10 g, and Canada uses 13.6 g. This calculator shows both the UK unit and the US standard drink side by side so you can use whichever your guideline is written in, and convert between them without doing the maths each time.

Alcohol also carries calories that many people overlook. Pure alcohol provides about 7 kilocalories per gram, almost as much as fat, so one UK unit (8 g) adds roughly 56 calories before you count any sugar or mixers. A large 250 ml glass of 13% wine is around 228 calories and a pint of beer can be 180 or more, which is why regular drinking can quietly undo a diet. Tracking units helps with health risk, while tracking the calories alongside helps with weight, and this tool surfaces both.

Knowing your units also helps you track against guidelines. UK health advice is to keep below 14 units a week, spread over three or more days with several drink-free days; 14 units is about six pints of average-strength beer or ten small glasses of low-strength wine. US guidance suggests up to one standard drink a day for women and two for men, with less always being safer. As a very rough rule the body clears about one unit per hour, but that average cannot tell you when you are safe or legal to drive, including the morning after a heavy night, because only time lowers blood alcohol and people clear it at different rates.

When to use it

• Working out how many units are in a pint, a glass of wine or a measure of spirits before you order.
• Adding up a whole evening or a week of drinks to compare against UK or US low-risk guidelines.
• Comparing a strong craft beer against an ordinary lager to see how much the higher ABV adds.
• Logging home pours and cocktails, where the glass size and strength are not standardised.
• Estimating the calories in a round so you can fit drinks into a daily or weekly calorie budget.
• Converting between UK units and US standard drinks when a guideline is written in the other system.

How to use the Alcohol Units Calculator

1. Enter the drink volume in millilitres (for example 568 for a UK pint, or 355 for a US 12 oz beer).
2. Enter the ABV percentage shown on the label or bottle.
3. Set how many of that identical drink you are having.
4. Or pick a common drink from the quick-fill menu to fill volume and ABV for you.
5. Read off the UK units, US standard drinks, grams of pure alcohol, calories, and the rough hours to clear.
6. Repeat for each different drink and add the units together to track a session or a week.

Formula & method

Worked examples

UK units, US standard drinks and calories for common drinks

How the reference amount differs by country

What 14 UK units a week looks like

Common mistakes to avoid

• Counting drinks instead of units. A large 250 ml glass of 13% wine is over 3 UK units, not 1. Counting glasses or bottles rather than units badly underestimates how much alcohol you have actually had.
• Assuming all beer or wine is the same strength. A 4% lager and an 8% craft beer in the same glass differ by double. Always check the ABV on the label, because strengths have risen and vary a lot between brands.
• Treating UK units and US standard drinks as equal. They are different scales. One US standard drink is about 1.75 UK units, so the same drink reads as a bigger number in UK units. Do not mix the two when tracking.
• Using the hours-to-clear figure to decide if you can drive. The roughly one-unit-per-hour rule is a crude average that ignores your weight, sex, food and health. It must never be used to judge whether you are safe or legal to drive, including the next morning.
• Forgetting the calories in alcohol. Pure alcohol has about 7 calories per gram, so a single unit is roughly 56 calories before mixers. A night out can add hundreds of calories that are easy to miss when counting only food.
• Believing coffee, water or sleep speeds up sobering up. Only time lowers blood alcohol. A cold shower, strong coffee or a few hours of sleep do not clear alcohol faster, so a big night can still leave you over the limit the morning after.

Glossary

ABV

Alcohol by volume, the percentage of a drink that is pure alcohol, printed on the label.

UK unit

A UK measure equal to 10 ml (about 8 g) of pure alcohol. Found as volume in ml times ABV percent divided by 1000.

US standard drink

A US measure equal to 14 g (about 0.6 fl oz) of pure alcohol, used to compare drinks of different sizes and strengths.

Pure alcohol (ethanol)

The intoxicating substance in drinks. Its density is about 0.789 g per ml, used to convert volume to grams.

Low-risk guidelines

Official advice on amounts that carry lower health risk, such as the UK limit of 14 units a week.

BAC

Blood alcohol concentration, the percentage of alcohol in the blood, often the legal measure for driving. It depends on body weight, sex and time, not just units.

Widmark formula

A common method for estimating BAC from the alcohol consumed, body weight, sex and time since drinking. It gives only an estimate.

Alcohol calories

Energy from the ethanol in a drink, about 7 calories per gram, separate from any sugar or mixer calories.

Frequently asked questions

Sources

• Alcohol units , NHS (UK National Health Service)
• What Is A Standard Drink? , U.S. National Institute on Alcohol Abuse and Alcoholism
• Alcohol Unit and Calorie Calculator , Drinkaware