One unit of alcohol equals 10ml (or 8g) of pure ethanol in the UK system. In the United States, the equivalent measure is called a “standard drink,” which is larger: 14 grams of pure alcohol, or about 0.6 fluid ounces. These numbers are the foundation for everything from drink labels to health guidelines, and knowing them helps you track what you’re actually consuming.
UK Units vs. US Standard Drinks
The confusion around alcohol units often comes from the fact that different countries define them differently. In the UK, one unit is 8 grams of pure alcohol. In the US, one standard drink contains 14 grams, nearly double the UK unit. So if you’re reading American health advice and it says “one drink per day,” that’s equivalent to about 1.75 UK units. This matters when you’re comparing guidelines across countries or reading labels from imported drinks.
How to Calculate Units in Any Drink
Every alcoholic drink has two pieces of information you need: the volume in milliliters and the ABV (alcohol by volume) percentage, which is printed on the label. The formula for UK units is simple:
Units = (volume in ml × ABV%) ÷ 1,000
So a 175ml glass of wine at 13% ABV works out to (175 × 13) ÷ 1,000 = 2.3 units. A pint of beer (568ml) at 4% ABV is (568 × 4) ÷ 1,000 = 2.3 units as well. A single 25ml measure of 40% spirits comes to exactly 1 unit.
This formula reveals something that catches many people off guard: a regular pint of beer and a medium glass of wine contain roughly the same amount of alcohol. The wine glass looks smaller, but the alcohol concentration is much higher.
Common Drinks and Their Unit Counts
- Pint of regular-strength beer or lager (4% ABV): about 2.3 units
- Pint of strong beer or lager (5.2% ABV): about 3 units
- Medium glass of wine, 175ml (13% ABV): about 2.3 units
- Large glass of wine, 250ml (13% ABV): about 3.3 units
- Single spirit measure, 25ml (40% ABV): 1 unit
- Double spirit measure, 50ml (40% ABV): 2 units
- Bottle of wine, 750ml (13% ABV): about 10 units
- Can of regular beer, 330ml (5% ABV): about 1.7 units
These are estimates. Craft beers, natural wines, and cocktails vary widely. A hazy IPA at 7% ABV in a pint glass contains nearly 4 units. Home pours of wine or spirits tend to be significantly larger than pub measures, sometimes double.
How Quickly Your Body Processes Alcohol
Your liver breaks down alcohol at a roughly fixed rate, regardless of your size, tolerance, or how much water you drink. The commonly cited figure is about one unit per hour, though individual metabolism varies. Coffee, cold showers, and food don’t speed up alcohol processing once it’s in your bloodstream. They might make you feel more alert, but your blood alcohol level drops at the same pace regardless.
This means a bottle of wine (10 units) shared between two people gives each person around 5 units, which takes roughly 5 hours or more to fully clear. If you finish drinking at midnight, you could still have alcohol in your system well into the next morning, something worth considering before driving.
Weekly Guidelines and What They Mean
The UK’s chief medical officers recommend no more than 14 units per week for both men and women, spread over three or more days rather than consumed in a single session. To put that in perspective, 14 units is roughly six pints of average-strength beer or six medium glasses of wine across an entire week.
That guideline is set at the level where the risk of alcohol-related illness stays relatively low. It doesn’t mean 14 units is “safe” in any absolute sense. The risk increases gradually with consumption, and there’s no completely risk-free level of drinking.
Calories in Alcohol Units
Pure alcohol contains 7 calories per gram, which puts it between carbohydrates (4 calories per gram) and fat (9 calories per gram). One UK unit, at 8 grams of pure alcohol, delivers 56 calories before you account for sugars, mixers, or anything else in the drink. A pint of beer at 2.3 units adds up to around 180 to 230 calories depending on the brew. A large glass of wine can top 200 calories easily. These are sometimes called “empty calories” because alcohol provides energy but virtually no nutritional value.
Why Serving Sizes Are Misleading
One of the biggest practical problems with alcohol units is that real-world servings rarely match the standard measures used in guidelines. A pub wine glass has grown from 125ml to 175ml or 250ml as the default in many places. Cocktails often contain two or three spirit measures. At home, people tend to pour wine glasses that hold 200ml or more without realizing it.
If you’re trying to track your intake accurately, measuring at home with a kitchen scale or measuring cup for a week can be eye-opening. Many people who believe they drink “a glass or two” per evening are actually consuming 4 to 5 units, which adds up to 28 to 35 units across a week, well above the recommended limit.