What is an alcohol unit?
A UK alcohol unit is 10ml, or 8g, of pure alcohol. That's roughly the amount an average adult can process in an hour. (NHS)
The catch is that very few drinks contain exactly one unit. The strength of the drink and the size of the glass both change the number, and pours at home are rarely measured.
How to work out the units in a drink
Multiply the volume in millilitres by the ABV, then divide by 1,000. A 175ml glass of wine at 13% is 175 × 13 ÷ 1,000, which comes to 2.3 units.
Why strength matters as much as size
Wine strengths vary more than most people realise. The same 175ml glass is about 2 units of an 11.5% Vinho Verde, but about 2.5 units of a 14.5% Malbec. Over a week of evening glasses, that difference adds up.
How many units are in a bottle of wine?
A 750ml bottle of wine at 13% contains just under 10 units. Shared between two people over dinner, that's about five units each, which is already more than a third of the weekly low-risk guideline.
Why units matter if you're cutting back
The UK's low-risk drinking guidelines are set in units, so knowing roughly how many are in your usual drink is the quickest way to see where you stand. See UK alcohol guidelines explained.