This estimates blood alcohol concentration using the Widmark formula, a well-known method for illustrating how alcohol, body weight, sex, and time affect BAC. It's built to help you understand the factors involved — not to help you calculate how close to a limit you can get.
BAC Estimator
LiveThe Widmark formula
r is a distribution ratio (≈0.68 for men, ≈0.55 for women) reflecting body water content, and 0.015 is a commonly used average elimination rate per hour.
A 180 lb man, 3 standard drinks over 2 hours: estimated BAC ≈ 0.046%. This is still an estimate — impairment (reaction time, judgment, coordination) can be affected well below this level, and individual results vary substantially.
Why this number can't tell you it's safe to drive
The Widmark formula is a population average — it doesn't account for how much food you've eaten, your individual metabolism, medications, or how your body specifically processes alcohol on a given day. Real BAC can run meaningfully higher or lower than this estimate for the same inputs. Cognitive and motor impairment also begins before commonly cited legal limits in most places. The only reliable way to know you're safe to drive is: don't drink at all before driving, or don't drive at all after drinking.
Frequently asked questions
Can I use this to check if I'm under the legal limit to drive?
No. This is an educational estimate, not a measurement, and real BAC can differ meaningfully from what a formula predicts. Never use an estimate to decide whether to drive — if you've had any alcohol, arrange another way home.
What factors does this formula not account for?
Food intake, drinking speed, medications, liver function, and individual metabolism all affect real BAC and aren't captured by this formula, which is why actual measured BAC (via breathalyzer or blood test) can differ from the estimate.
What should I do if I or someone else has had too much to drink?
Arrange a safe way home that doesn't involve driving, keep the person hydrated and in a safe position, and seek emergency medical help immediately for signs of alcohol poisoning — confusion, vomiting, slow or irregular breathing, seizures, difficulty staying conscious, or bluish or pale skin.
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