BAC Calculator (Blood Alcohol Level & Sober Time)
Estimate blood alcohol concentration from standard drinks, body weight, sex, and elapsed time using the Widmark formula — with hours to zero and legal limit context.
BAC Calculator — interactive calculator, computed instantly in your browser.
Blood Alcohol Calculation: The Widmark Formula and Its Limits
42 g ÷ (0.68 × 81.6 kg) ÷ 10 = 0.076% — minus 0.015% per hour
Estimates vary widely between people — never a basis for deciding whether to drive
Blood alcohol concentration rises with alcohol consumed and body water, then falls as the liver clears it at a roughly fixed rate. This calculator applies the Widmark formula with sex-specific factors, weight, drink count, and elapsed hours, reporting estimated BAC, total ethanol in grams, hours until zero, and status against common legal limits — strictly educational arithmetic.
1. The Widmark Formula
- One standard drink carries about 14 grams of pure ethanol (12 oz beer, 5 oz wine, 1.5 oz spirits)
- The Widmark factor r is 0.68 for males and 0.55 for females, reflecting body-water differences
- Division by 10 converts grams per kilogram into the percent figure used in legal limits
- Hydration and body composition shift results — fat tissue holds less water to dilute alcohol
2. Elimination: The Fixed Rate
- The liver clears about 0.015% per hour — near one standard drink, and it does not accelerate
- Coffee, cold showers, and food after drinking do not raise elimination; only time does
- The time-to-zero card divides starting BAC by 0.015 to project full sobriety
- Recovery inputs pair naturally with the 💧 Water Intake Calculator for hydration planning
3. Legal Limits in Context
- 0.08% is the US per-se driving limit; 0.05% covers most of Europe, Australia, and Canada
- Impairment begins measurably well below either limit — reaction and judgment degrade early
- Commercial drivers and underage drivers face much lower or zero-tolerance thresholds
- The status card turns color as the estimate crosses each threshold — for education only
4. What the Estimate Cannot Capture
Food in the stomach, drinking speed, tolerance, medications, and individual enzyme variation all move real BAC away from any formula. A number on a screen is never a green light to drive — arrange transport in advance. Sleep quality affects how recovered you feel the next morning, which the 😴 Sleep Calculator can help schedule even if it cannot remove the remaining alcohol.
🔗 Recovery & Body Estimates
Alcohol is calories with a pharmacology — the estimate here is educational arithmetic, not a driving decision. Keep hydration inputs straight with the 💧 Water Intake Calculator or the whole ❤️ Health & Fitness Hub.
Sleep is when the body finishes clearing the rest — check tonight's cycles with the 😴 Sleep Calculator.
Frequently Asked Questions (BAC Calculator)
Within roughly twenty percent for healthy adults when inputs are honest — but real-world spread is wide. Food, hydration, drinking pace, tolerance, and metabolism all shift the true value, so treat the output as an illustration, never a measurement.
The liver clears about 0.015% per hour, so starting from 0.08% takes over five hours to reach zero. The time-to-zero card computes it from your estimate — doubling the drinks doubles the wait, and nothing accelerates the rate itself.
About 14 grams of pure ethanol: 12 ounces of 5% beer, 5 ounces of 12% wine, or 1.5 ounces of 40% spirits. Craft beers, pours, and cocktails often exceed one standard drink, which is the most common undercount in self-estimates.
No. Elimination happens in the liver at a fixed rate that neither caffeine nor activity changes. Time, hydration, and food before drinking are the only meaningful levers — and even those affect the rise, not the clearance speed.