What is the Widmark formula?

BAC = (Alcohol grams / (body weight grams × r)) × 100 − (elimination rate × hours). The distribution ratio 'r' is 0.68 for males and 0.55 for females. Elimination averages 0.015% BAC per hour.

How accurate is this?

Not very. Food in stomach, hydration, medication, body composition, genetics, and drink strength all change BAC significantly. Treat the result as a rough indicator, never as a green light to drive.

What BAC level is the legal limit?

Most US states: 0.08%. Utah: 0.05%. Many countries (Germany, France, most of Europe): 0.05%. Commercial drivers and drivers under 21 often face 0.02% or zero tolerance. Check your local law.

What is a 'standard drink'?

In the US: 14 g of pure alcohol — roughly a 12 oz (355 ml) 5% beer, 5 oz (148 ml) 12% wine, or 1.5 oz (44 ml) 40% spirit. The preset options use these benchmarks.

Can I use this to decide whether to drive?

No. Never. This tool is for post-hoc curiosity only. If you drank any alcohol, don't drive — use a taxi, rideshare, or wait well past the calculator's 'back to zero' estimate.

BAC Calculator (Blood Alcohol)

Health & Fitness· 11 tools

Free Blood Alcohol Content (BAC) calculator. Enter your sex, weight, drinks consumed, and time elapsed since drinking to estimate your current BAC using the classic Widmark formula. Estimates only — individual factors (food, medication, metabolism) cause large variation. Never rely on a calculator to decide whether to drive.

Sex

Units

Body weight (kg)

Drinks consumed

Beer (12 oz, 5%)

Wine (5 oz, 12%)

Spirit (1.5 oz, 40%)

Hours since first drink

Estimated BAC

0.029%

Relaxed

Peak BAC

0.059%

Time to sober

1.9h

Not medical advice. Do not use to decide whether to drive.

Widmark formula is a rough estimate. Food, medication, genetics, and metabolism cause wide variation.

Frequently Asked Questions

References

Widmark formula — Alcohol and the Law — National Center for Biotechnology Information
What is a standard drink? — NIAAA

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Frequently Asked Questions

References and sources

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