BAC Estimator
Estimates your Blood Alcohol Content (BAC) using the Widmark formula, adjusted for sex, body weight, number of drinks, and time since drinking began.
1 standard drink = 14 g pure alcohol (12 oz beer, 5 oz wine, 1.5 oz spirits)
Formula
Widmark Formula:
BAC (g/dL) = [A / (W × r)] × 100 − (β × t)
- A = total alcohol consumed (grams) — 14 g per US standard drink
- W = body weight (grams)
- r = Widmark distribution factor — 0.68 (male), 0.55 (female)
- β = alcohol elimination rate — 0.015 g/dL per hour (average)
- t = hours since drinking began
BAC is floored at 0 (cannot be negative).
Assumptions & References
- One US standard drink contains 14 grams of pure ethanol (NIAAA definition).
- Widmark r values: 0.68 for males, 0.55 for females (Widmark, 1932; updated by Posey & Mozayani, 2007).
- Average alcohol elimination rate (β) is 0.015 g/dL/hr; actual range is 0.010–0.020 g/dL/hr depending on the individual.
- The formula assumes alcohol is fully absorbed. Food, carbonation, and drinking speed affect absorption rate and are not modeled here.
- Legal BAC limit for driving in the US is 0.08 g/dL; limits vary by country and driver category.
- This tool is for educational purposes only and should not be used to make decisions about driving or safety.
- References: Widmark EMP (1932); NIAAA Standard Drink Definition; Posey & Mozayani, Forensic Science, Medicine, and Pathology (2007).