How long does it take for alcohol to leave your system?

The short answer

The NHS describes roughly one UK unit per hour as an average adult processing rate. A UK unit is 10 ml, or about 8 g, of pure alcohol. Individuals can differ substantially, so counting units does not identify the moment your blood alcohol reaches zero.

Example: two 330 ml drinks at 5% ABV contain 3.3 UK units. Dividing by the average rate gives about 3.3 hours of processing for the total dose. This is not a countdown from the last drink; absorption and metabolism overlap during drinking.

What the calculator measures

1. Enter the actual serving volume and ABV from the label for each beverage.
2. Multiply ml × ABV ÷ 1000 × servings to get UK units. Add different drinks together.
3. Read the average processing duration as an educational illustration, not a personal clearance time.

UK units differ from standard-drink definitions used in other countries. This tool does not estimate blood alcohol concentration or test detection windows. Tests may detect alcohol or its metabolites, and their methods and thresholds differ.

Why a fixed time cannot tell you it is safe

Metabolism varies with biology, liver function, medicines and other factors. Drink size and self-reported intake may also be inaccurate. Feeling better does not prove alcohol is gone. Coffee or a shower does not provide a reliable shortcut.

Do not use the result to decide when to drive, operate machinery, take medication or pass a test. For a medicine question, ask a pharmacist or clinician. If someone is unconscious, having a seizure, or breathing slowly or irregularly after drinking, contact local emergency services immediately. Do not wait for a calculator result.

Sources

NHS: Alcohol units — https://www.nhs.uk/live-well/alcohol-advice/calculating-alcohol-units/

NIAAA: Alcohol metabolism — https://www.niaaa.nih.gov/publications/alcohol-metabolism

NHS: Alcohol poisoning — https://www.nhs.uk/conditions/alcohol-poisoning/