Blood Alcohol Content (BAC) Calculator
Estimate blood alcohol content from drinks consumed, body weight and time elapsed.
Assumptions used in this calculation
- Educational estimate only: This is a rough estimate for educational purposes, never use it to judge fitness to drive. Individual metabolism varies significantly.Widmark formula (Widmark, 1932)
About this calculator
Guessing whether you've had "too much" to drink is unreliable, alcohol's effect on blood alcohol content depends on body weight, sex, how much you drank, and how much time has passed, factors that interact in ways that are hard to track mentally after a few drinks. This calculator applies the Widmark formula, the standard method behind most BAC estimation tools, using standard drinks consumed, body weight, gender, and hours elapsed since the first drink: it converts drinks into grams of alcohol, divides by body weight times a sex-specific distribution constant, then subtracts an elimination rate of about 0.015% per hour for the time that's passed. The gender input matters because the distribution constant differs by sex, women's bodies typically have a higher fat-to-water ratio, which concentrates the same amount of alcohol in a smaller fluid volume. This is a rough educational estimate only, actual BAC is affected by food intake, drink strength, and individual metabolism the calculator can't measure, never use it to judge fitness to drive.
Worked example
70kg, 2 drinks, 1 hour
Result: ≈0.044% BAC
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