16% at 150 ml — 18.9 g of pure alcohol

“One drink” differs by country

A US drink is 1.77 times a UK unit and 1.4 times a WHO drink. So a single 500 ml beer at 5% is 2.5 units in Britain, 2.0 drinks by the WHO count, and 1.4 in the US. The same beer is honestly “two and a half” and “one and a half” at once. Comparing national guidance without accounting for this gap gets the numbers wrong.

Strength and volume trade off exactly

Halve the strength and double the glass and the alcohol is unchanged. 4% at 500 ml equals 8% at 250 ml, and a 5% can of beer lands near a 40% shot. That is why “it is only a weak drink” does not hold up unless you also count the size of the glass.

Same strength, other volumes

Same volume, other strengths

Britain and America define it by volume

A UK unit is 10 ml of pure alcohol; a US drink is 0.6 fl oz, which is 17.7 ml. Both are volumes, so you multiply by the ethanol density of 0.789 to get a weight — 7.89 g and 14.0 g, which is where the familiar 8 and 14 come from. Because the British definition is a volume, litres × ABV gives units directly: a 750 ml bottle of 12% wine is exactly 9 units.

The calories here count the alcohol only

A gram of alcohol yields 7 kcal — above carbohydrate and protein at 4, below fat at 9. The figure here counts the alcohol alone, so it excludes the carbohydrate in beer, the sugar in sweeter drinks, and anything mixed in. The real calorie count is higher.

How to read it

• Pure alcohol (g) = volume (ml) × strength (%) ÷ 100 × 0.789.
• Strength is a volume fraction, so multiplying by the volume gives the volume of alcohol.
• Multiply that by the ethanol density, 0.789, and you have a weight.
• A UK unit is 10 ml of pure alcohol — which is why litres × ABV gives units directly.
• A US drink is 0.6 fl oz (17.7 ml); a WHO drink is 10 g.
• A gram of alcohol is 7 kcal, and this chart counts the alcohol only.

No drinking limits are printed here

Low-risk drinking guidelines differ a great deal between countries, and several have revised theirs downward in recent years. Printing a number here would go stale, so this chart gives only the measurement. For how much is appropriate, check the current health guidance where you live, and talk to a doctor if you have a condition or take medication.