What the percentage on the label tells you
A 5% ABV beer contains approximately 5 ml of alcohol in each 100 ml of beer. A 40% spirit contains approximately 40 ml per 100 ml. The label describes concentration, not the total amount in your glass. That is why comparing drinks by ABV alone can be misleading.
To find the volume of pure alcohol, multiply the serving volume by ABV divided by 100. For a 330 ml beer at 5%, this is 330 × 0.05 = 16.5 ml. To express that as UK units, divide by 10: 1.65 units. For other countries' standard drinks, convert the pure alcohol to grams and use the relevant definition.
Why serving size can reverse a comparison
A 330 ml beer at 7% contains 23.1 ml of alcohol. A larger 500 ml beer at 5% contains 25 ml. The lower-strength beer has slightly more alcohol in the serving because there is more of it. Neither the drink name nor the percentage alone gives the full picture.
The same issue appears with wine: a small pour and a large pour from the same bottle have identical ABV but different alcohol amounts. When you repeat a template, confirm the portion as well as the product. It is easy to keep an accurate strength and accidentally reuse an inaccurate volume.
| Example | Pure alcohol | UK units |
|---|---|---|
| 330 ml beer at 7% | 23.1 ml | 2.31 |
| 500 ml beer at 5% | 25 ml | 2.50 |
| 150 ml wine at 12% | 18 ml | 1.80 |
| 250 ml wine at 12% | 30 ml | 3.00 |
| 50 ml spirit at 40% | 20 ml | 2.00 |
For cocktails, add the alcoholic ingredients
If you know the recipe, calculate each alcoholic ingredient separately and add the results. A fictional mixed drink containing 50 ml of 40% spirit has 20 ml of pure alcohol, or 2 UK units. Adding 150 ml of a non-alcoholic mixer does not change those 2 units. It changes the total volume and concentration.
For a two-ingredient example, take 30 ml of 40% spirit and 30 ml of 20% liqueur. The first contributes 12 ml of alcohol and the second 6 ml, giving 18 ml in total, or 1.8 UK units. Water, soda and melted ice add no alcohol. An alcoholic mixer, wine or second liqueur does contribute and must be counted.
If the final mixed volume were exactly 200 ml, the first example would be approximately 10% ABV: 20 ÷ 200 × 100. Actual final volume can be uncertain, especially with ice. For logging the alcohol consumed, the known ingredient amounts are usually more useful than a guessed finished-cocktail ABV.
Handle an unknown pour without inventing precision
A menu may name a cocktail without giving the recipe, measures or strength. Ask for serving information when practical, or record an estimate based on the details you do have. Mark it as estimated in your own record. Do not assume every drink with the same name uses the same recipe.
If the uncertainty is meaningful, keep a range in your review instead of treating a guessed decimal as a fact. For example, a 25 ml versus 50 ml pour of 40% spirit changes the result from 1 to 2 UK units. That is a much larger difference than whether the result displays one or two decimal places.
Do not reuse an uncertain restaurant cocktail as a precise template for every venue. Templates work best when the recipe and portion are repeatable. A measured home recipe and a menu name are different kinds of information.
Check units before entering the volume
Millilitres, litres and fluid ounces are not interchangeable labels. A 0.5 litre serving is 500 ml, not 0.5 ml. US and UK fluid ounces also differ: approximately 29.57 ml and 28.41 ml respectively. Select the correct system in the calculator instead of entering an ounce value into a millilitre field.
For packaged drinks, use the package volume and the fraction consumed. For a shared bottle, log your own portion rather than the full bottle. Avoid counting the bottle and its individual servings in the same record, which duplicates the alcohol amount.
Save the inputs, not only the calculated total
Keep the drink name, serving volume and ABV alongside the date. That makes later corrections understandable. If a product changes from 5% to 6%, you can see why two similarly named entries should not use the same calculation. If only a total was saved, the original assumption is harder to reconstruct.
AlcoList's drink templates can hold repeat serving details so that you do not have to rebuild them each time. Use the app for a consistent record, and use the calculator when you want to check an unfamiliar serving. Neither an ABV calculation nor a log estimates when it is safe to drive, measures blood alcohol, or assesses personal medical risk.
The short version
ABV is a concentration. Pair it with the amount consumed, add each alcoholic ingredient in a mixed drink, and keep uncertainty visible when the recipe or pour is unknown.
