How long until your BAC is back to 0.00?

The body clears alcohol at a roughly constant rate of about 0.015% BAC per hour once absorption is complete, regardless of how much was drunk — so a BAC of 0.08% takes roughly 5 to 6 hours to reach 0.00%, not the "one hour per drink" shorthand people often repeat.

Why "one drink per hour" is a rough floor, not a rule

That shorthand happens to be close to correct for a single average-weight adult and one standard drink, but it breaks down fast: body weight, biological sex, how much was eaten, and how the drinks were spaced all shift the actual BAC produced by the same number of drinks. The elimination rate itself (~0.015%/hour) is fairly consistent across healthy adults, but the peak BAC it's counting down from is not.

The formula behind the estimate

ExactCalcs' BAC calculator uses the textbook Widmark formula — BAC = (A × 5.14 / (W × r)) − (0.015 × H) where A is alcohol in ounces, W is body weight in pounds, r is a sex-specific distribution ratio, and H is hours since the first drink. It's the standard formula taught in toxicology and used across forensic and educational contexts; calculator.net's page (a common reference point) doesn't publish a formula at all, which is part of why it's worth showing the actual math here.

What the estimate doesn't account for

• Individual metabolism, medication, and health conditions can shift elimination rate meaningfully.
• Food in the stomach slows absorption but doesn't change the total alcohol absorbed.
• Legal limits (0.08% in most US states) are a legal threshold, not a safety threshold — impairment starts well below it.

Treat any BAC estimate as directional, not a substitute for waiting longer than the number suggests, or not driving at all.