If you have ever looked at a drink and wondered how much alcohol it actually contains, the answer is usually two label details away. You need the serving volume and the alcohol by volume, or ABV. Once you have both, a simple calculation turns a vague description such as “one beer” or “a glass of wine” into a more useful number.
This guide explains how to calculate alcohol units for almost any drink. You will see the formula, worked examples, a practical chart, and the limits of what a unit calculation can tell you. The goal is clearer tracking, not a promise that a number can measure impairment or make a drinking decision for you.
How to calculate alcohol units
The UK alcohol-unit formula is:
Alcohol units = volume in millilitres × ABV percentage ÷ 1,000
ABV is the percentage printed on the bottle, can, menu, or drinks list. Use the number as written: 5% ABV is entered as 5, not 0.05. Volume is the amount of liquid you actually drink, not necessarily the size of the container.
For example, a 440 ml can at 5% ABV contains:
440 × 5 ÷ 1,000 = 2.2 units
The same formula works for wine, beer, cider, spirits, and a mixed drink. A 175 ml glass of wine at 13% ABV contains 175 × 13 ÷ 1,000, or 2.275 units, which is normally rounded to about 2.3 units.
One UK unit represents 10 ml, or about 8 grams, of pure alcohol. That definition makes drinks with different volumes and strengths easier to compare. It does not mean that every glass, bottle, or can equals one unit.
What the ABV label is telling you
ABV means alcohol by volume. A drink labelled 12% ABV is 12% pure alcohol by volume. It does not tell you the total number of units on its own because the amount you drink matters too.
Consider two glasses:
- 125 ml of wine at 12% ABV = 1.5 units
- 250 ml of wine at 12% ABV = 3 units
The wine has the same strength, but the larger glass contains twice as much alcohol. Now compare two 500 ml cans:
- 500 ml at 3.5% ABV = 1.75 units
- 500 ml at 7% ABV = 3.5 units
The volume is identical, but the stronger drink contains twice as many units. This is why “number of drinks” is a rough measure. Volume and strength are the details that make the difference.
If the label shows alcohol as a range, use the stated value for the product you actually have. If you do not know the ABV or the serving size, record the drink as an estimate and mark it as approximate rather than creating false precision.
Worked examples for common drinks
Beer or cider
A 330 ml bottle of beer at 5% ABV contains:
330 × 5 ÷ 1,000 = 1.65 units
A 568 ml UK pint of lager at 4% ABV contains:
568 × 4 ÷ 1,000 = 2.272 units
That is about 2.3 units. A stronger pint at 5.2% ABV contains about 3 units. The word “pint” describes the volume, not the strength, so two pints can have very different totals.
For a 500 ml can of cider at 6% ABV:
500 × 6 ÷ 1,000 = 3 units
Flavoured, premium, and strong ciders can contain more alcohol than a person expects from the can size. Check the label every time you switch products.
Wine
A 750 ml bottle of wine at 13% ABV contains:
750 × 13 ÷ 1,000 = 9.75 units
That is commonly rounded to about 9.8 or 10 units. A 14% bottle of the same size contains 10.5 units. A 175 ml glass from a 13% bottle contains about 2.3 units, while a 250 ml glass contains 3.25 units.
The familiar phrase “a glass of wine” is therefore not a reliable unit. A small home pour, a pub measure, and a large restaurant pour can all be different volumes.
Spirits
A 25 ml measure of 40% spirit contains:
25 × 40 ÷ 1,000 = 1 unit
A 50 ml double contains 2 units at the same strength. A 35 ml measure at 40% ABV contains 1.4 units. Measures vary by country and venue, so use the actual pour when you can.
Cocktails
Cocktails are harder because they may contain more than one alcoholic ingredient. Calculate each ingredient separately, then add the results.
Suppose a drink contains 50 ml of gin at 40% ABV and 25 ml of a 20% liqueur:
- Gin: 50 × 40 ÷ 1,000 = 2 units
- Liqueur: 25 × 20 ÷ 1,000 = 0.5 units
- Total alcohol: 2.5 units, before any additional alcoholic ingredients
Ice, soda, juice, and other mixers change the drink’s total volume but do not remove the alcohol that was poured. If a cocktail uses a free pour or an unknown measure, the result is an estimate.
A quick alcohol-units table
The examples below are illustrations, not universal serving values. Always check the volume and ABV of the specific product.
| Drink | Volume | ABV | Approximate units |
|---|---|---|---|
| Beer bottle | 330 ml | 5% | 1.65 |
| Beer can | 440 ml | 5% | 2.2 |
| Pint of lager | 568 ml | 4% | 2.3 |
| Wine glass | 175 ml | 13% | 2.3 |
| Large wine glass | 250 ml | 13% | 3.25 |
| Wine bottle | 750 ml | 13% | 9.75 |
| Single spirit | 25 ml | 40% | 1 |
| Double spirit | 50 ml | 40% | 2 |
You can use the Alcohol Units Calculator to test the exact volume and ABV for a drink. For a different measurement system, the Standard Drink Calculator helps explain why a UK unit and a US standard drink are not interchangeable labels. The UK alcohol units guide adds the weekly-guideline and drink-free-day context.
How to track units without overcomplicating it
The most useful record is usually the one you can keep consistently. A practical entry includes:
- The date and approximate time.
- The drink type or product name.
- The serving volume.
- The ABV from the label.
- The number of servings.
- Whether the amount was measured or estimated.
If you drink two identical cans, calculate one can and multiply the result by two. If you have different drinks, calculate each separately and add them. Rounding to one decimal place is usually enough for personal tracking; carrying many decimal places can make the record look more exact than the inputs really are.
It also helps to record drinks soon after you have them. Memory tends to compress a mixed evening into “a few,” especially when pours differ. A diary or app can preserve the serving details while the label is still nearby. Alcohol Tracker° lets you record serving size and ABV alongside the drink so the calculated total remains connected to the original entry.
What calculating units cannot tell you
Units measure the amount of pure alcohol in a drink. They do not measure blood alcohol concentration, intoxication, dependence, or whether someone is safe to drive. BAC depends on factors such as body composition, drinking pace, food, medicines, health, and time. A unit total should never be used as a driving test.
The UK Chief Medical Officers’ guidance says that if adults choose to drink, they should not regularly exceed 14 units per week, spread over three or more days. That is a population-level low-risk guideline, not a personal guarantee or a target that everyone should reach. People who are pregnant, taking certain medicines, managing a medical condition, or worried about their drinking should get advice from a qualified health professional.
If you drink heavily every day or experience shaking, sweating, anxiety, or other withdrawal symptoms when you stop, speak to a medical professional before making a sudden change. The NHS specifically advises getting medical advice in that situation.
Frequently Asked Questions
What is the formula for alcohol units?
Multiply the drink volume in millilitres by its ABV percentage, then divide by 1,000. For example, 500 ml at 5% ABV is 500 × 5 ÷ 1,000 = 2.5 units.
Is one drink the same as one unit?
No. A “drink” can mean many different serving sizes and strengths. A 25 ml measure of 40% spirit is one UK unit, but a 175 ml glass of 13% wine is about 2.3 units.
Does a unit tell me if I am safe to drive?
No. Units tell you how much alcohol was in a drink, not your BAC or impairment. Never use an alcohol-unit calculation to decide whether to drive.
How accurate is an alcohol-unit calculator?
The arithmetic can be accurate when the volume and ABV are accurate. The result becomes an estimate when the pour, product strength, or serving size is unknown. Record the inputs and keep the rounding sensible.
Where can I check the official guidance?
See the NHS guidance on drinking less, the Alcohol Change UK unit calculator, and Drinkaware’s guide to alcohol units.
The takeaway
To calculate alcohol units, multiply volume in millilitres by ABV and divide by 1,000. That one formula works for a can, a bottle, a glass, a shot, or a multi-ingredient cocktail. The important part is using the drink you actually poured rather than a generic serving assumption.
Once the calculation becomes a habit, tracking is less about guessing and more about noticing patterns. Use the number as context, keep the original serving details visible, and treat health guidance as guidance rather than a measurement of safety.
Keep exploring
Use the calculator or continue with a related guide:
Put the guide into practice
Keep a clearer drink diary.
Track units, standard drinks, cost, calories, dry days and estimated BAC on iPhone and Apple Watch.
