Blood Alcohol (BAC) Estimator
Estimate blood alcohol concentration from drinks, body weight, sex and time with the Widmark formula — for education only, never to decide whether to drive.
For general information only — not medical advice. Results are estimates; talk to a doctor or qualified health professional about your own health.
How to use
- 1Enter the number of standard drinks, your weight and sex.
- 2Enter the hours since your first drink.
How it's calculated
BAC (%) = alcohol (g) ÷ (body weight (g) × r) × 100 − 0.015 × hours, with r = 0.68 for men and 0.55 for women. A US standard drink contains 14 g of alcohol.
Frequently asked questions
Can I use this to decide if I can drive?
No. Real BAC varies with food, medication, health and drink strength. The only safe choice is not to drive after drinking.
What is a standard drink?
In the US, 14 g of pure alcohol: about 12 oz of 5% beer, 5 oz of 12% wine or 1.5 oz of 40% spirits. UK units are 8 g.
What are legal driving limits?
0.08% in most of the US, 0.05% in much of Europe and Australia, and lower (or zero) for young and commercial drivers.