What Counts as One Drink? The Standard Drink in the US, UK, Australia and Canada

Order “one drink” in New York, London and Sydney and you are using three different units of measurement without knowing it. Every country that publishes drinking guidelines defines a standard drink — a fixed amount of pure alcohol — and then counts everything in it. The trouble is that they do not agree on how big that amount is, and almost nothing anyone actually pours is exactly one of them.

This matters for two reasons. A health guideline that says “no more than X drinks” only makes sense in its own country’s unit. And a BAC estimate built on “number of drinks” is only as good as the assumption about what a drink is.

The Standard Drink, Country by Country

Grams per standard drink as used by Alcophone for each country. Volumes are what holds exactly one, at 0.789 g of alcohol per ml. The UK defines its unit by volume, as 10 ml of pure alcohol (7.9 g); the rounded 8 g used here puts its volumes a few ml higher than that definition.

In the US, the National Institute on Alcohol Abuse and Alcoholism (NIAAA) defines a standard drink as 14 grams of pure alcohol — the amount in a 12 oz beer at 5%, a 5 oz glass of 12% wine or a 1.5 oz shot of 40% spirits. Canada’s Guidance on Alcohol and Health uses 13.45 grams, which is a 341 ml bottle of 5% beer. Australia’s National Health and Medical Research Council (NHMRC) and Ireland’s Health Service Executive (HSE) both use 10 grams.

The UK is the odd one out twice over. It calls the measure a “unit” rather than a standard drink, and at about 8 grams it is the smallest of the group: a US standard drink holds roughly 1.75 UK units. India has no official national definition at all; Alcophone uses 10 grams there, the same size as Australia and Ireland.

Why a Pint Is Rarely One Drink

The reference drinks in the table above are smaller and weaker than what most bars and most kitchens actually serve. Here is what common servings come to in each country’s unit.

Counts rounded to one decimal. Alcohol content assumes the ABV shown; check the label of what you are actually drinking.

Two things stand out. First, size: a UK or Irish pint is 568 ml, more than half as big again as a 12 oz can, so even an ordinary 5% lager is 2.8 UK units or 1.6 US standard drinks. A 250 ml “large” glass of wine is a third of a bottle and counts as 3.0 units. Second, strength: craft beer at 7% or more turns a 16 oz pint into almost two US standard drinks, and the large peg common in India is about two Australian-size drinks in a single glass.

This is also why the labels are not as helpful as they look. Australian alcohol labels state the number of standard drinks, and many UK labels show units, but US labels do not — and a label can only describe the bottle or can, not the size of the glass someone fills from it.

How to Count Any Drink Yourself

You need two numbers from the label or the menu: the volume and the ABV. Then:

• Pure alcohol (ml) = volume (ml) × ABV ÷ 100
• Pure alcohol (g) = pure alcohol (ml) × 0.789
• Standard drinks = grams ÷ your country’s standard drink (14 in the US, 13.45 in Canada, 10 in Australia and Ireland)

Worked example: a 16 oz (473 ml) pint of 7% IPA. 473 × 7 ÷ 100 = 33.1 ml of pure alcohol. 33.1 × 0.789 = 26.1 g. In the US that is 26.1 ÷ 14 = 1.9 standard drinks; in Australia, 2.6; in the UK, 3.3 units.

The UK has a faster route, because its unit is defined as 10 ml: units = volume (ml) × ABV ÷ 1,000. A 568 ml pint of 5% lager is 568 × 5 ÷ 1,000 = 2.8 units, which is the same answer as going through the grams (22.4 g ÷ 8).

Same Number of “Drinks”, Very Different Amounts of Alcohol

Because the units differ, “I had four” means a different amount of alcohol in each country. Here is what four drinks over two hours does to estimated BAC when each drink is one country’s standard drink, with everything else held the same.

Illustrative estimates from Alcophone’s model (Jackson 2002 body-fat + Norberg distribution, sex- and age-based elimination at the empty-stomach rate). Profiles: 220 lb man, 6 ft, 40; 180 lb man, 5 ft 10, 30; 140 lb woman, 5 ft 5, 30; 120 lb woman, 5 ft 3, 25. Fasted, four drinks spread over two hours, BAC at the last drink. The same model in every column; only the size of a drink changes.

Four UK units are only about 57% of the alcohol in four US standard drinks, and the BAC follows. A guideline, a rule of thumb like “one drink an hour” or a friend’s “I only had four” cannot be compared across borders until you know whose drink it is counting.

The Low-Risk Guidelines Are Not the Same Either

Weekly grams are the weekly limit multiplied by that country’s standard drink. The US guidance is stated per day; its weekly figure here is the daily one times seven, for comparison.

• United States: the NIAAA and the CDC describe drinking in moderation as up to 2 drinks a day for men and up to 1 for women, and both say that drinking less is better for health than drinking more.
• Canada: Canada’s Guidance on Alcohol and Health (2023) treats risk as a continuum rather than a limit. Risk is low at a couple of drinks a week, moderate up to 6, and increasingly high beyond that, and it advises no more than 2 on any one occasion.
• United Kingdom: the UK Chief Medical Officers advise no more than 14 units a week for men and women alike, spread over three or more days rather than saved up for one or two.
• Australia: the NHMRC advises no more than 10 standard drinks a week and no more than 4 on any one day.
• Ireland: the HSE’s low-risk guidelines are 17 standard drinks a week for men and 11 for women, with no more than 6 on one occasion and some alcohol-free days each week. They are under review in 2026.
• India: there is no official national low-risk guideline.

Measured in grams, the spread is wide: the UK’s 14 units are 112 g a week, close to Australia’s 100 g, while Canada’s 6 drinks are about 81 g. None of these numbers is a safe amount — every one of the agencies above says that less is better — and none of them is about driving. They describe long-term health risk, not how much you can drink and still be under a legal limit an hour later.

What Alcophone Does With This

Alcophone does not estimate BAC from a count of standard drinks. Every drink you log carries its real volume and ABV, so a 568 ml pint of 5% lager and a 355 ml can of 4.2% light beer go into the model as the different amounts of alcohol they are. The standard-drink count is only how the total is shown to you, and it follows your country: standard drinks in the US, Canada, Australia, India and Ireland, units in the UK.

Its standard-drink sheet also shows your country’s low-risk guideline, and the app checks your estimated BAC against the legal driving limit where you are — which, like the size of a drink, is not the same everywhere.

The Practical Version

• “One drink” is a unit, not a glass: 14 g in the US, 13.45 g in Canada, 10 g in Australia and Ireland, about 8 g in the UK.
• A pint, a large glass of wine and a craft beer are each usually two or more of them — a 5% UK pint is 2.8 units.
• To count any drink: volume × ABV ÷ 100 × 0.789 gives grams; divide by your country’s standard drink. In the UK, volume × ABV ÷ 1,000 gives units directly.
• Read a guideline in the unit of the country that wrote it, and remember that low-risk is not no-risk.
• No guideline and no count tells you whether you can drive. Never drive after drinking.

Frequently Asked Questions

What is a standard drink?

A fixed amount of pure alcohol that a country uses as its unit for counting drinks — not a particular glass. In the US it is 14 grams, in Canada 13.45 grams, in Australia and Ireland 10 grams, and in the UK the “unit” is 10 ml, about 8 grams. A 12 oz beer at 5% is one US standard drink; the same can is 1.4 Australian standard drinks.

How many units are in a pint?

A UK pint (568 ml) of 5% lager is 2.8 units. The quick way to work it out is millilitres × ABV ÷ 1,000: 568 × 5 ÷ 1,000. A pint of 6% craft beer is 3.4 units — so a single pint of something strong can be close to a quarter of the UK’s 14-unit weekly guideline.

Is a UK unit the same as a US standard drink?

No. A US standard drink holds 14 g of alcohol and a UK unit about 8 g, so one US drink is roughly 1.75 UK units. Turned around, the UK guideline of 14 units a week is about 8 US standard drinks. Two people can both say “I had four” and be describing very different amounts of alcohol.

Full limit tables by country: USA (50 states + DC) · Canada · Australia · United Kingdom · India · Ireland