Blood Alcohol (BAC) Calculator
Widmark estimate of blood alcohol content from sex, weight, standard drinks and hours — with a hard rule: never drive after drinking.
Reviewed by the OmniCalc teamMethod verified 2026-07-01
1 standard drink = 14 g pure alcohol
0.0365% BAC
= 0.02–0.08% — impaired; do not drive= 28 g pure alcohol
Estimated blood alcohol 0.0365 percent — 0.02–0.08% — impaired; do not driveShow steps
- Alcohol: 2 drinks × 14 g = 28 g of pure alcohol.
- Widmark: BAC = 28 g ÷ (80 kg × 1000 × r 0.68) × 100 = 0.051471%.
- Elimination: 0.015% × 1 h = 0.015%. Estimate: BAC ≈ 0.051471% − 0.015% = 0.036471%.
Rough estimate only — real BAC varies widely between individuals. Never drive after drinking. This is not legal or medical advice.
How to use the BAC calculator
- 1Pick your sex — it sets the Widmark ratio (r = 0.68 male, 0.55 female).
- 2Enter your weight in kilograms and the number of standard drinks — 1 drink = 14 g of pure alcohol.
- 3Set how many hours have passed since the first drink — each hour lowers the estimate by about 0.015%.
- 4Read the estimate and its interpretation, with the full calculation under Show steps.
Never drive after drinking
This is a rough estimate only— real BAC depends on food, medication, genetics and health, so individual variation is large and your true value can be well above the number shown. Never use it to decide whether you’re fit to drive: if you have been drinking, don’t drive at all. This tool is not legal or medical advice.
Frequently asked questions
How is BAC estimated here?
With the Widmark formula: BAC% = alcohol in grams ÷ (body weight in kg × 1000 × r) × 100, minus about 0.015% for each hour since the first drink. The ratio r is 0.68 for males and 0.55 for females.
What counts as one standard drink?
One standard drink is 14 g of pure alcohol — roughly 355 ml of 5% beer, 150 ml of 12% wine, or 44 ml of 40% spirits. Count a strong cocktail as more than one drink.
How accurate is this estimate?
It is a rough population average. Real BAC depends on food, medication, genetics, hydration and drinking pace, so your true value can differ a lot. Only a breath or blood test measures actual BAC — never use this tool to decide whether you can drive.
How fast does BAC go down?
On average about 0.015% per hour, and nothing meaningfully speeds it up — coffee, cold showers and exercise do not sober you up. Only time removes alcohol from the blood.