Definitions around the world

Alcohol units and standard drinks

“One drink” is not a fixed amount of alcohol. Serving size and strength both matter, and countries use different definitions for a unit or standard drink.

By the HeelClick team · 6 minute read · Reviewed 6 September 2026 · Editorial standards

Quick answerA UK unit contains 10 ml or about 8 g of pure alcohol. A US standard drink contains 14 g, an Australian standard drink contains 10 g and a Canadian standard drink contains 13.45 g. Use the definition for the country whose guidance you are following.

How to calculate the alcohol in a serving

Start with the serving volume and alcohol by volume, or ABV. A 500 ml beer at 5% ABV contains 25 ml of pure alcohol. That equals 2.5 UK units, but the standard-drink result is different under definitions based on grams. Check the label and serving size because venue measures, cans and glasses vary.

Use the free alcohol units and standard drinks calculator to choose a national definition and total one serving or several drinks.

Why the national definition matters

The NHS explains UK units, the US National Institute on Alcohol Abuse and Alcoholism explains US standard drinks, the Australian Government explains Australian standard drinks, and the Canadian Centre on Substance Use and Addiction explains the Canadian definition. These measures help compare servings, but lower-risk guidance also varies by country and can change. Check current official advice where you live.

Alcohol measures cannot assess impairment or give permission to drive. Read why a calculator cannot tell you if you can drive.

Why a drink count can mislead

  • A double spirit is still one glass but contains twice the measure.
  • A strong craft beer may contain far more alcohol than a lower-strength lager of the same size.
  • A large wine glass may hold more than one standard serving.
  • Cocktails can contain several measures without making that obvious.

Use one consistent definition

A night-out drink limit can support an immediate plan, while units or standard drinks can help you compare servings over time. Do not mix national definitions in one total. None of these numbers can calculate impairment or tell you whether driving is safe. Medication, health conditions and pregnancy can also change what advice applies, so use professional guidance where relevant.

What HeelClick tracks

HeelClick lets you log drinks inside a night-out plan that also covers time, spending and the journey home. It does not calculate blood alcohol concentration or provide a medical assessment.

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