How to Count Alcohol Units

Alcohol math matters more than most drinkers realize. A “glass of wine” can mean 125ml at 11% ABV or 250ml at 14.5% — nearly triple the alcohol for the same name. If you want to stay inside health guidelines, track your tolerance, or just know what you’re actually drinking, you need a consistent unit. The UK uses “units” (10ml of pure alcohol), the US uses “standard drinks” (14g of pure alcohol), and bartenders use neither. This guide gives you the formulas, the thresholds, and the quick mental shortcuts so you can count accurately no matter what’s in your glass.

1. The UK unit formula

One UK unit = 10ml (8g) of pure ethanol. The formula is simple:

units = (ABV% × volume in ml) / 1000

A 175ml glass of 13% wine: 13 × 175 / 1000 = 2.275 units. A pint (568ml) of 5% lager: 5 × 568 / 1000 = 2.84 units. A 25ml shot of 40% spirits: 40 × 25 / 1000 = 1.0 unit. The math is the same for every drink — only the ABV and volume change.

2. The US “standard drink”

The US defines one standard drink as 14g (17.7ml) of pure alcohol. That’s roughly 1.75 UK units. The typical US rules of thumb:

• 12 oz (355ml) of 5% beer = 1 standard drink
• 5 oz (148ml) of 12% wine = 1 standard drink
• 1.5 oz (44ml) of 40% spirits = 1 standard drink

These are designed to roughly match. In reality, a craft IPA at 7.5% ABV in a 16oz pour is closer to 2 standard drinks, not one.

3. Weekly guidelines

The UK Chief Medical Officers recommend no more than 14 units per week, spread over 3+ days, with several alcohol-free days. The US Dietary Guidelines suggest no more than 2 standard drinks per day for men and 1 for women — roughly 14 and 7 per week respectively. The WHO position is blunter: no level of alcohol is safe for health. These numbers are ceilings, not targets.

4. Wine math is where most people lose count

Wine bottles come in 750ml. At 13% ABV that’s 13 × 750 / 1000 = 9.75 UK units per bottle, or ~5.5 US standard drinks. A “large” 250ml restaurant pour of 14% wine is 3.5 units — a quarter of your weekly cap in one glass. New World reds and whites routinely hit 14-15% ABV; older European wines sit closer to 11-12%. Always check the label.

5. Beer math by strength tier

Beer ABV ranges from ~3% (light lager) to 12%+ (imperial stouts). Quick table for a UK pint (568ml):

• 3.5% session bitter: 2.0 units
• 4.5% standard lager: 2.6 units
• 5.5% craft pale ale: 3.1 units
• 7.5% IPA: 4.3 units
• 10% imperial stout: 5.7 units

A single strong IPA pint can exceed a full glass of wine. “Just one pint” isn’t a fixed dose.

6. Spirits and cocktails

A UK pub measure is 25ml (some pubs pour 35ml). A US shot is typically 1.5oz (44ml). Most spirits sit at 37-40% ABV. A gin & tonic with a 25ml gin pour is 1 unit; a double is 2. Cocktails often contain 50-90ml of spirits across multiple ingredients — a Long Island Iced Tea can hit 4-5 units in a single glass. When you can’t see the pour, assume more.

7. Shortcut mental math

For fast estimation, memorize these:

• Pint of 4% beer = 2.3 units
• Small (125ml) 12% wine = 1.5 units
• Medium (175ml) 13% wine = 2.3 units
• Large (250ml) 14% wine = 3.5 units
• Single spirit (25ml, 40%) = 1 unit

Round up when you’re unsure. Underestimating is the default failure mode.

8. Converting UK units to US drinks

One US standard drink = 1.75 UK units. To convert:

US drinks = UK units / 1.75
UK units = US drinks × 1.75

UK weekly cap of 14 units = roughly 8 US standard drinks. US daily cap of 2 drinks = 3.5 UK units. Same ethanol, different packaging.

9. Time and blood alcohol

Your liver processes about one unit per hour (one US standard drink every ~90 minutes). If you drink 4 units in an hour, you’re carrying 3 units’ worth of alcohol into the next hour. Food slows absorption but doesn’t reduce the total. Coffee doesn’t sober you up — only time does.

10. Common mistakes

• Using “glasses” instead of ml. Home pours are 30-50% bigger than restaurant pours. Measure once to calibrate your eye.
• Ignoring ABV creep. Craft beer and New World wine have drifted stronger over the last decade. A 2015 IPA and a 2026 IPA are not the same drink.
• Counting cocktails as “one drink.” Count the spirits in each cocktail and add them up. A margarita is usually 2 units, not 1.
• Forgetting non-drinking days. The UK guideline is 14 units spread over 3+ days. Ten units on Saturday is not the same as 2 per day.
• Trusting “low-cal” labels. A low-calorie beer can still be 5% ABV. Calorie count and alcohol content are independent.

11. Run the numbers

Plug in the ABV and volume of your actual drink rather than guessing. Then pair it with your daily calorie math — alcohol is 7 kcal/g, second only to fat.

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