🍺 BAC Calculator
Estimate your Blood Alcohol Content (BAC) using the Widmark formula. This is an educational estimate only.
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Warning: This is an educational estimate only, not a precise or medical measurement. BAC is affected by many factors this tool cannot account for. Never drive after drinking — if you plan to drink, arrange a sober ride home. When in doubt, don't get behind the wheel.
How the BAC Calculator Works
This calculator uses the Widmark formula, a well-known method for estimating blood alcohol content from the amount of alcohol consumed, body weight, sex, and time elapsed.
Formula
BAC% = (alcohol grams / (body weight in grams × r)) × 100 − (0.015 × hours)
r (Widmark constant) = 0.68 for men, 0.55 for women
Result is clamped at a minimum of 0%
This calculator is for educational purposes only and should never be used to decide whether it is safe to drive or operate machinery. Actual BAC depends on many factors including food intake, metabolism, medications, and drink strength, which this tool cannot measure. Never drive after drinking alcohol.
Frequently Asked Questions
Is this BAC calculator accurate enough to know if I can drive?
No. This tool provides a rough educational estimate only. Actual BAC varies significantly based on factors like food intake, medications, and individual metabolism. Never use an estimate to decide whether it's safe to drive — the only safe choice after drinking is not to drive.
What counts as a "standard drink"?
In the US, a standard drink contains about 14 grams of pure alcohol — roughly a 12 oz beer, a 5 oz glass of wine, or a 1.5 oz shot of spirits.
Why does BAC decrease over time in the formula?
The body metabolizes alcohol at a roughly steady rate, commonly estimated at about 0.015% BAC per hour, which the formula subtracts based on hours elapsed since drinking began.