Blood Alcohol Calculator

Estimate using the Widmark formula. Educational only. Never use this to decide if you can drive — always err on the side of "no."

Estimated BAC

Right now

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Legal limit (US driving)

0.08%

Status

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Impairment level

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Hours until 0.00%

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This is an estimate. Period.

Real BAC depends on dozens of factors this calculator can't see: food in stomach, exact alcohol absorption rate, medications, fatigue, individual liver enzyme genetics, hydration, and how recently you ate. Your actual BAC can be ±30% from this number.

The legal limit for driving in most US states is 0.08%. Utah is 0.05%. Many countries are lower or zero. Commercial drivers and underage drivers have stricter limits.

The math (Widmark, 1932)

BAC = (g alcohol) / (body mass × distribution) × 100 − 0.015 × hours

Distribution ratio: 0.68 for men, 0.55 for women (women have proportionally less body water on average, so the same drinks produce higher BAC). The 0.015%/hour subtraction is the average ethanol metabolism rate — your liver clears alcohol at this approximate steady pace.

Plan for zero

If there's any chance you'll need to drive, drink water and stop early. Better: have a plan that doesn't involve driving at all (rideshare, designated driver, public transit). The downside of "I think I'm fine" is unforgivable; the downside of "I called an Uber" is twelve dollars.