Health Formula • Published on July 30, 2026 • Last updated August 09, 2026
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Total grams of pure alcohol = Volume (mL) × ABV% × 0.789 (alcohol density), summed across all drinks
Widmark factor for body water distribution: 0.68 for men, 0.55 for women
Hours elapsed since drinking began, used to subtract metabolized alcohol at 0.015%/hour
The Widmark formula estimates Blood Alcohol Concentration by dividing the total grams of alcohol consumed by body weight adjusted for a gender-based body-water distribution constant, then subtracting the amount the body has already metabolized over elapsed time at an average elimination rate. It is widely used to give a rough estimate of impairment level, though it is not a substitute for an actual breathalyzer or blood test.
Women generally have a higher proportion of body fat and lower body water content than men at the same weight, so alcohol becomes more concentrated in their bloodstream — the Widmark r-factor (0.55 vs 0.68) accounts for this difference.
No — this is only an estimate. Actual BAC is affected by many factors not captured here (food intake, medication, metabolism, drink strength variability), so it should never be used to decide whether it's safe or legal to drive.
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