Blood Alcohol Content Estimator
Add your drinks, enter your body weight and time since first drink, and get an estimated BAC using the Widmark formula with a clear drive-limit verdict. This is an estimate only - never drive after drinking. Data never leaves your browser.
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Drinks
Estimated BAC
This is an estimate based on the Widmark formula. Individual metabolism varies. NEVER use this to decide whether to drive. Alcohol affects judgement, reaction time, and coordination at all detectable levels.
Learn more: how BAC is estimated, its limits, and FAQ
How BAC is calculated
This calculator uses the Widmark formula: BAC = (alcohol in oz × 5.14) ÷ (body weight in lbs × body water constant) - (0.015 × hours since the first drink). The body water constant is approximately 0.73 for males and 0.66 for females, reflecting average differences in body water distribution. The result is an estimated blood alcohol percentage at a given point in time, not a measured one.
Why this is an estimate, not a measurement
The Widmark formula is a population average - actual BAC depends on factors it can't see: how fast you drank, whether you ate, medications, liver function, and individual metabolism. Two people with identical inputs can have meaningfully different real BAC. Never use this calculator, or any estimate, to decide whether it's safe to drive.
FAQ
How long does it take for BAC to reach zero?
The average elimination rate is approximately 0.015% BAC per hour. Someone at 0.09% BAC would take roughly 6 hours to reach zero. Individual metabolism varies with liver health, food consumed, and medications, so the calculator's time estimate is a guide, not a guarantee.
What is the legal drink-drive limit?
The UK and most US states use 80mg per 100mL blood (0.08% BAC). Scotland, most EU countries, and Australia use 50mg per 100mL (0.05% BAC). The calculator shows estimated time until under both thresholds.