Blood Alcohol Calculator

Estimate your blood alcohol content (BAC) using the Widmark formula — the standard scientific method based on body weight, biological sex, standard drinks consumed, and hours elapsed. This is an educational estimate, not a legal or medical measurement: individual results vary widely. Runs entirely in your browser.

Body weight

Weight unit

Biological sex

Hours since first drink

Beers 12 oz at 5% = 1 standard drink

Glasses of wine 5 oz at 12% = 1 standard drink

Shots of spirits 1.5 oz at 40% = 1 standard drink

Other standard drinks enter directly if you counted yourself

⚠️ Never drive after drinking — use a sober driver, taxi, or rideshare. This calculator is an educational estimate based on averages. Real BAC depends on food, medications, metabolism, drink strength (craft beer and cocktails vary enormously), and more. You can be legally and physically impaired below any calculator's estimate. If you feel any effects at all, do not drive.

Frequently Asked Questions

How is BAC calculated?

This calculator uses the Widmark formula: BAC% = (A × 5.14) ÷ (W × r) − 0.015 × H. A is ounces of pure alcohol (standard drinks × 0.6 oz), W is body weight in pounds, r is the body-water ratio (0.73 for males, 0.66 for females), and H is hours since the first drink — your body metabolizes roughly 0.015% BAC per hour. It's the same formula used in forensic estimates, but with averages, not your personal biology.

What counts as one standard drink?

In the U.S., one standard drink contains about 0.6 fluid ounces (14 grams) of pure alcohol: 12 oz of regular beer at 5%, 5 oz of wine at 12%, or 1.5 oz of distilled spirits at 40%. Watch out for stronger pours — craft IPAs, double shots, and stiff cocktails can be 1.5–2.5 standard drinks each, which makes every BAC estimate less reliable.

What is the legal BAC limit for driving?

In all 50 U.S. states except Utah, 0.08% is the per se DUI limit for drivers 21+; Utah's limit is 0.05%. Commercial drivers face a 0.04% limit, and drivers under 21 face zero-tolerance limits (typically 0.00–0.02%). But you can be arrested for impaired driving below the limit if an officer observes impairment — the limit is a ceiling, not a safe target.

How long until I'm sober?

On average, BAC falls about 0.015% per hour — and nothing speeds that up. Not coffee, not cold air, not food, not exercise. Only time. A 0.08% BAC takes roughly 5+ hours to clear. When in doubt, wait longer than the estimate, or don't drive at all.

Why does sex matter in the formula?

Alcohol distributes through body water, and females typically have a lower percentage of body water than males at the same weight — hence the different r values (0.66 vs 0.73). The same number of drinks therefore produces a higher BAC on average for females. It's a population average, not a rule about any individual.

Can I rely on this instead of a breathalyzer?

No. A calculator estimate is not evidence of sobriety. Even an accurate breathalyzer only measures this moment — alcohol from your last drink may still be absorbing, pushing your BAC higher after you test. If there's any doubt, get a ride.