Estimate your current blood alcohol concentration (BAC), time to sober, and impairment level using the Widmark formula. Includes hourly BAC timeline and effects reference.
Blood alcohol concentration (BAC) determines your level of impairment andegal driving status. While only a breathalyzer or blood test can measure BAC precisely, the Widmark formula provides a well-studied pharmacokinetic estimate based on the amount of alcohol consumed, body composition, and elapsed time since drinking — useful for planning safe transportation or understanding your impairment level.
The human body eliminates alcohol at a remarkably constant rate of approximately 0.015% BAC per hour (range: 0.012–0.020%), regardless of weight, tolerance, or how much was consumed. This means the only thing that truly lowers BAC is time — not coffee, cold showers, food, or exercise. Understanding this rate allows you to estimate when you will reach sobriety or fall below the legal driving limit.
This calculator uses the Widmark formula (BAC = grams of alcohol / (body weight × distribution ratio)) with first-order elimination kinetics, adjusted for biological sex (which affects the volume of distribution), food consumption (which delays absorption), and elapsed time. It provides an hourly BAC timeline, impairment description, and time estimates for reaching both 0.08% (legal limit) and 0.00% (complete sobriety).
Understanding your estimated BAC helps you make safer decisions about driving, work, and activities requiring coordination. One in three traffic fatalities involves alcohol, and many occur when drivers believe they are "fine to drive." This calculator provides objective estimates to counter the unreliable self-assessment that impaired judgment produces — because alcohol impairs the very judgment needed to assess impairment.
Peak BAC = (grams of alcohol) / (body weight in grams × Widmark r) Widmark r: Male = 0.68, Female = 0.55 Standard drink = 14 g pure alcohol Current BAC = Peak BAC − (0.015 × hours elapsed) Time to sober = Current BAC / 0.015
Result: Current BAC ≈ 0.047% — below legal limit, mild impairment
Three standard beers = 42g alcohol. Peak BAC = 42 / (80,000 × 0.68) = 0.077%. After 2 hours of elimination (0.015 × 2 = 0.030%), current BAC ≈ 0.047%. Below the 0.08% legal limit but still impaired. Estimated sober in ~3.1 more hours.
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BAC calculators provide rough estimates (±20-30% of true BAC). Individual variation in liver enzyme activity, genetics (ADH/ALDH variants), medications, health conditions, and drinking speed all affect actual BAC. Never make driving decisions based on a calculator — when in doubt, don't drive.
No. Coffee may make you feel more alert, but it does not reduce BAC or actual impairment. Only time removes alcohol from your body. A wide-awake drunk driver is still a drunk driver. The elimination rate is fixed at ~0.015%/hour.
Biological females typically have a higher ratio of body fat to water than males. Since alcohol distributes in water but not fat, the same amount of alcohol produces a higher concentration in a smaller volume of body water, resulting in a higher BAC at the same body weight and consumption.
One standard drink contains 14 grams of pure alcohol: 12 oz of 5% beer, 5 oz of 12% wine, or 1.5 oz of 40% spirits. Many craft beers (7-10% ABV), wine pours (6-8 oz), and cocktails with multiple spirits contain 1.5-3+ standard drinks each.
Yes, significantly. Food in the stomach delays gastric emptying and alcohol absorption, lowering and delaying peak BAC by 1-2 hours. This doesn't reduce total alcohol absorbed — it just spreads absorption over more time, allowing concurrent elimination. Eating after drinking has minimal effect.
No. Impairment begins at 0.02% BAC. The 0.08% limit is a legal threshold, not a safety threshold. Crash risk doubles at 0.05% and increases 11-fold at 0.08%. Many countries use 0.05% or even 0.02% as the legal limit. Commercial driver limits in the US are 0.04%.