Why does gender affect the BAC estimate?

The Widmark formula uses a body-water distribution constant (r) that differs by sex, roughly 0.68 for men and 0.55 for women, because women's bodies typically have a higher proportion of fat to water, which concentrates alcohol in a smaller fluid volume.

Can I use this number to decide if I'm okay to drive?

No. This is a rough educational estimate, actual BAC is affected by food intake, drink strength, metabolism, and other factors this calculator can't measure precisely. Never use it to judge fitness to drive, use a certified breathalyzer or simply don't drive after drinking.

Blood Alcohol Content (BAC) Calculator

Estimate blood alcohol content from drinks consumed, body weight and time elapsed.

How this is calculated

Widmark formula: BAC‰ = Alcohol grams ÷ (Weight kg × r); subtract 0.015%/hour elimination

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.

About this calculator

The BAC calculator estimates blood alcohol content using the Widmark formula, based on standard drinks consumed, body weight, gender and hours elapsed since the first drink.

Worked example

70kg, 2 drinks, 1 hour

Result: ≈0.044% BAC

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Blood Alcohol Content (BAC) Calculator

About this calculator

Frequently asked questions

Why does gender affect the BAC estimate?

Can I use this number to decide if I'm okay to drive?