🍷Blood Alcohol Calculator

About this tool

Choose your sex, enter body weight and hours since your first drink, then add drinks from the list — beer, wine, spirits, cider, seltzer, cocktails. The estimate shows the BAC, grams of alcohol, UK units and US standard drinks, and roughly how long the body takes to clear it, with a clear warning.

How BAC is estimated — and why you can't rely on it

The Widmark formula, from the 1930s and still the basis of forensic estimates, divides the grams of alcohol drunk by body weight times a distribution ratio — about 0.68 for men and 0.55 for women, reflecting body water — and subtracts about 0.015% for each hour since drinking began. A 175 ml glass of 13% wine is about 18 g of alcohol (2.2 UK units). What the estimate is good for is understanding: why the same drinks hit a lighter person harder, why women typically reach higher levels than men on the same drinks, and how slowly alcohol leaves — coffee, water, food after the fact and sleep do not speed elimination. What it cannot do is tell you whether you are safe or legal to drive. Real levels vary by up to ±50% with food, medication, liver health and how fast you drank, and legal limits differ: 0.08% in most of the US, Canada and England and Wales, 0.05% in Scotland, Australia and most of Europe, and lower or zero for new drivers. The only safe level for driving is zero. Not medical or legal advice. The caffeine calculator models the same idea for coffee, the water intake calculator covers hydration, and the sleep calculator plans the night.

Frequently asked questions