The sum
The NHS gives it in one line: strength multiplied by volume in millilitres, divided by 1,000. A unit is 10ml of pure alcohol, so all the sum is doing is counting how many 10ml measures of alcohol are in the glass.
A British pint is 568ml. The law is fussier than that, 568.26ml by the Weights and Measures Act, but the extra quarter of a millilitre never moves the answer at one decimal place. So for a pint the sum comes down to the strength times 0.568. A 4.6% lager works out as 4.6 × 568 ÷ 1,000, which is 2.6 units.
The NHS rounds its own examples to whole numbers: 2 units for a pint at 3.6%, and 3 for a pint at 5.2%. Worked to one decimal those come out at 2.0 and 3.0, so nothing much is lost at either end. It matters more in the middle: a pint at 4.5% is 2.6 units, and calling that 3 is out by nearly half a unit.
By strength and by pack
| Strength | Pint | 440ml can | 500ml can | 330ml bottle | 660ml bottle |
|---|---|---|---|---|---|
| 3.4% | 1.9 | 1.5 | 1.7 | 1.1 | 2.2 |
| 4.0% | 2.3 | 1.8 | 2.0 | 1.3 | 2.6 |
| 4.5% | 2.6 | 2.0 | 2.3 | 1.5 | 3.0 |
| 4.8% | 2.7 | 2.1 | 2.4 | 1.6 | 3.2 |
| 5.0% | 2.8 | 2.2 | 2.5 | 1.7 | 3.3 |
| 5.5% | 3.1 | 2.4 | 2.8 | 1.8 | 3.6 |
The column people get wrong is the can. A lot of supermarket lager comes in 440ml cans, which is 128ml short of a pint, and it is easy to count a can as a pint. It isn't. Four 440ml cans of 4.6% lager come to 8.1 units; four pints of the same beer would be 10.5.
The 660ml bottle catches people out in the other direction, because it is more than a pint. The one pack on this site that makes the sum easy is the pint can: Stella Artois comes in 568ml cans, so the pint column is the can column.
The same beer, fewer units
This is the part the unit calculators don't tell you. A pint of a foreign lager bought in Britain is often not the same strength as a pint of it at home, so it doesn't carry the same units either. The figures below use the strength on the British pack and the strength the brewer gives for its home market, both sourced on each beer's own page.
| Beer | UK | At home | Units a pint, UK | Units a pint, at home |
|---|---|---|---|---|
| Amstel | 3.4% | 5.0% | 1.9 | 2.8 |
| Grolsch Premium Pilsner | 3.4% | 5.0% | 1.9 | 2.8 |
| Carlsberg Danish Pilsner | 3.4% | 4.6% | 1.9 | 2.6 |
| Beck's | 4.0% | 4.9% | 2.3 | 2.8 |
| Kronenbourg 1664 | 4.6% | 5.5% | 2.6 | 3.1 |
| Coors Lager | 3.4% | 4.2% | 1.9 | 2.4 |
| Estrella Galicia Especial | 4.7% | 5.5% | 2.7 | 3.1 |
| Stella Artois | 4.6% | 5.2% | 2.6 | 3.0 |
| Budweiser | 4.5% | 5.0% | 2.6 | 2.8 |
| Cruzcampo Sevilla | 4.4% | 4.8% | 2.5 | 2.7 |
| San Miguel Especial | 5.0% | 5.4% | 2.8 | 3.1 |
| Guinness Draught | 4.1% | 4.2% | 2.3 | 2.4 |
The biggest gap here is Amstel: 3.4% in Britain against 5.0% in the Netherlands. That is 1.9 units a pint here and 2.8 there, so every British pint of it carries 0.9 fewer units.
Guinness Draught is in that table too, at 4.1% on the British cans on record against 4.2% from the brewer. The Guinness section below has the units for both, and for the rest of the range.
Several of these sit at exactly 3.4%, which is not a coincidence. UK duty more than doubles at 3.5%, and the guide to the duty threshold sets out the sums. Some of the beers are brewed here to the lower strength and some are imported and still come in weaker. If you drink the same brand on holiday, the British pint has been doing you a small favour.
How many pints is 14 units?
The NHS advises men and women not to drink more than 14 units a week on a regular basis, spread over three or more days. How many pints that is depends entirely on the beer. At 3.4% it is 7.2 pints. At 4% it is 6.2, at 5% 4.9, and at 5.5% 4.5.
The spread is wider than it looks. Between a 3.4% lager and a 5.5% one, both pale, both fizzy, both served in the same glass, the difference is 2.8 pints over a week, which is a good reason to look at the strength rather than go by the look of the thing.
How many units are in a pint of Guinness?
A pint of Guinness Draught is 2.3 units at the 4.1% listed for British cans, and 2.4 at the 4.2% Guinness gives on its own website. A 440ml can is 1.8 either way. The sum is the same as for any other beer.
Two strengths, two answers
Guinness's own list of strengths gives Draught at 4.2%, and the Draught page on its website says the same. Work the sum at that strength and you get 2.4 units a pint. The British cans are a tenth of a point lower: Tesco, Sainsbury's and Ocado all list Guinness Draught at 4.1%, which gives 2.3 units a pint. The Guinness Draught page has the small print and the listings. One older Tesco listing for the 4 x 440ml pack still shows 4.2%.
We haven't picked between them. Both come from Guinness or from its own packaging, and the gap comes to about 0.06 of a unit a pint. If you are counting a can you have bought, read the can: it has the strength on it, and the sum takes ten seconds. The guide to reading a can says where to look.
Units in each Guinness
| Beer | Pack | Strength | Units in the pack | Units in a pint |
|---|---|---|---|---|
| Guinness Draught, British can | 440ml can | 4.1% | 1.8 | 2.3 |
| Guinness Draught, Guinness's figure | 440ml can | 4.2% | 1.8 | 2.4 |
| Guinness Extra Stout | 440ml can | 4.2% | 1.8 | 2.4 |
| Guinness Foreign Extra Stout | 325ml | 7.5% | 2.4 | 4.3 |
| Guinness 0.0 | any | 0.0% | less than 0.1 | less than 0.1 |
Pack sizes are the ones on the retailer listings behind each beer's page. The Foreign Extra Stout figure is for the 4 x 325ml pack. A full pint of it is shown only to keep the columns alike.
The can, the four-pack and the week
The 440ml can is the pack most people take home, and it is 128ml short of a pint. At either strength it comes to 1.8 units. A four-pack is 7.2 units at 4.1% and 7.4 at 4.2%. That is just over half of the NHS advice of no more than 14 units a week on a regular basis, or 6.0 pints of Draught at 4.1% and 5.9 at 4.2%.
Extra Stout, Foreign Extra Stout and 0.0
The stout sold as Guinness Original or Extra Stout is 4.2% on the British listings on record, so a pint is 2.4 units and a 440ml can 1.8. Foreign Extra Stout is a different drink at 7.5%. One 325ml serving is 2.4 units, about the same as a whole pint of Draught in a much smaller glass. The 4 x 325ml pack on record also says it is brewed under licence in Nigeria; its page has the small print. Guinness 0.0 is 0.0% on the retailer listing and 0% on Guinness's own list, so there is nothing worth counting: less than 0.1 units a pint.
A pint in a pub
The tables here are for packs. A pub pint comes from a keg, and this site records what is printed on supermarket packs, so it has no strength on record for the keg. If the pub's Guinness is the same strength as the can, the pint figures above apply. If you know it isn't, the sum is the same: the strength times 0.568.
Units won't tell you if you can drive
The drink-drive limit isn't set in units. It is a level of alcohol in your breath, blood or urine, and it is lower in Scotland than in the rest of the UK. GOV.UK is plain about it: "it's impossible to say exactly how many drinks this equals". Units count what went into the glass, not what is in you an hour later, and weight, food and how fast you drink all move the answer.
The number for your beer
Every beer on this site shows its units a pint next to its strength, worked out from the strength on the British pack. Where a pack has been read, the units are given for that pack as well: a Heineken 440ml can is 2.2 units and the 330ml bottle 1.7. The figures are never rounded to whole numbers, and they change when the strength does. Start from the full list, or see every beer on the shelf by strength.