Glossary · Law and labelling
Drink-drive limit
Definition
The maximum blood, breath or urine alcohol concentration at which a person may lawfully drive. In the United Kingdom the limit in Scotland is lower than in England, Wales and Northern Ireland.
- Subject
- Law and labelling
In more detail
No arithmetic converts a number of drinks into a safe concentration for an individual: absorption and elimination vary with body composition, food, sex, medication and time. CiderHQ publishes the structure of the law and no formula purporting to predict compliance.
Related terms
Terms that belong to the same part of the subject, or that this one is routinely confused with.
Law and labelling
Unit of alcohol
The United Kingdom measure of alcohol consumed: one unit is 10 ml, or 8 grams, of pure ethanol. Units are calculated as volume in litres multiplied by ABV.
Law and labelling
Alcohol by volume
The proportion of a drink’s volume that is pure ethanol at 20 degrees Celsius, expressed as a percentage. It is the figure labelling law requires on drinks above 1.2 per cent.
Law and labelling
Standard drink
A national reference quantity of alcohol used in health guidance. It is not internationally consistent: a United States standard drink contains 14 grams of ethanol against the United Kingdom unit’s 8.
Where to go next
- Cider glossary — The whole vocabulary, by subject and A–Z.
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Sources
What this page rests on. Where a source is marked as registered rather than read, CiderHQ is recording that the body is authoritative on the subject without claiming to have worked through the document itself. See our evidence policy for what each state means.
GOV.UK · government · passage verified 2026-08-24
Read on 2026-08-24. The address CiderHQ had registered, gov.uk/drink-driving-law, now returns 404; the page is at gov.uk/drink-drive-limit and the record is corrected. Two things it establishes matter here. The limit is set at constituent-country level rather than at state level — Scotland’s is materially lower than England, Wales and Northern Ireland’s — which is the clearest single justification for modelling the four countries separately under the United Kingdom. And the page states plainly that no arithmetic converts drinks into a blood alcohol level for an individual, which is why CiderHQ’s unit calculator will not attempt one.