Blood Alcohol Content (BAC) Calculator
Estimate blood alcohol content from drinks, body weight, and time using the Widmark formula.
A textbook estimate, not a measurement — food, medication, tolerance, and individual metabolism all cause real BAC to differ from this formula. Never use this to decide whether it's safe to drive. If you've been drinking, don't drive — call a ride instead.
Estimated BAC
0.069%
Impaired
For informational and educational purposes only — not medical advice, and not a substitute for consulting a qualified professional about your specific situation. TrueMeasureKit is not liable for decisions made based on these results. See our Terms of Service.
The Widmark formula, and why it's only an estimate
Published by Erik Widmark in 1932, this formula estimates blood alcohol content from the amount of alcohol consumed, spread through an estimated fraction of body weight (the "Widmark r factor," which differs by sex because of typical differences in body water content), then subtracts a flat average elimination rate of 0.015% per hour. A "standard drink" — 12oz of regular beer, 5oz of wine, or 1.5oz of 80-proof spirits — contains roughly 14 grams of pure alcohol. Real BAC varies with food in the stomach, medications, hydration, and individual metabolism, sometimes substantially, which is why this is useful for general education about how alcohol accumulates and clears, but not for judging whether it's safe to drive or perform any task requiring full sobriety.
Frequently asked questions
What is the Widmark formula?
A standard method estimating blood alcohol content from the amount of alcohol consumed, body weight, biological sex (which affects body water distribution), and time elapsed since drinking started, as the body metabolizes alcohol at a roughly steady rate.
Is this calculator accurate enough to decide if I can drive?
No — actual BAC is affected by factors this formula can't fully capture, like food intake, medications, and individual metabolism, and legal limits carry serious consequences. Never use an estimate to decide whether it's safe to drive; the only safe choice after drinking is not to.