Estimate blood alcohol concentration from drinks, body weight, sex and time elapsed using the Widmark formula.
How bac is worked out
The Widmark formula estimates BAC from the alcohol consumed relative to body water, then subtracts roughly 0.015 per hour for metabolism. It is the basis of most online BAC estimates.
It is an estimate only, and a rough one. Food, medication, drinking speed, individual metabolism and body composition all shift the real figure — sometimes substantially. It should never be used to decide whether to drive.
Getting your answer
- Enter your body weight and sex.
- Enter the number of standard drinks.
- Enter the hours since your first drink.
The maths behind it
A worked example
As an example, with a hours since first drink of 2, the calculator returns a estimated BAC of 0.05%. Underneath, Peak BAC before metabolism comes out at 0.08% and Alcohol metabolised at 0.03%. Change any field and every figure updates as you type.