Alcohol Clearance Calculator
This calculator estimates your blood alcohol concentration (BAC) hour by hour using the Widmark formula. Alcohol clears at roughly 0.015 BAC per hour regardless of weight — but peak BAC depends heavily on body weight, sex, and how fast you drink. The model is for educational use only; do not use it to decide whether to drive.
One US standard drink = 14 g pure alcohol = 12 oz of 5% beer, 5 oz of 12% wine, or 1.5 oz of 40% spirits.
How the Widmark formula works
The Widmark equation estimates blood alcohol concentration from body weight, sex, and amount consumed. BAC = (alcohol grams × 100) / (body weight grams × Widmark factor r). The 'r' factor accounts for body composition — about 0.68 for males and 0.55 for females, reflecting differences in body water percentage. The model assumes alcohol distributes evenly in body water; fat tissue holds less alcohol than muscle, so leaner bodies show higher BAC for the same dose.
Linear vs first-order elimination
Alcohol clearance is unusual — it follows zero-order kinetics in most people, not first-order like caffeine. That means BAC falls at a constant rate (~0.015 per hour) rather than halving each half-life. Heavy chronic drinkers metabolise slightly faster (0.02 per hour); the elderly slightly slower. The constant-rate clearance is why doubling the dose roughly doubles the sober-up time.
Legal driving limits worldwide
United States: 0.08 BAC (commercial drivers: 0.04). Most of Europe: 0.05. Sweden, Norway, Poland: 0.02. UK (England, Wales, NI): 0.08. UK (Scotland): 0.05. Australia, Canada: 0.05 or 0.08 depending on province. Many countries impose zero-tolerance (0.00) for drivers under 21 or in commercial vehicles. The calculator output shows where you sit relative to common thresholds, but the only safe driving level after any alcohol is 0.00.
Why this calculator is for education only
Real BAC varies by 30–40% from the Widmark estimate at typical drinking levels. Food in the stomach delays peak BAC and reduces it slightly. Hydration affects body water proportion. Genetics shift ADH and ALDH enzyme activity by factors of 2 or more. Medications and illness change clearance. The Widmark formula is correct on average but no individual is average. Never rely on a BAC calculator for any decision involving safety or law.
Frequently asked questions
How long does alcohol stay in your system?
BAC drops at about 0.015 per hour for most people. A peak BAC of 0.08 takes about 5 hours to fully clear;…
BAC drops at about 0.015 per hour for most people. A peak BAC of 0.08 takes about 5 hours to fully clear; 0.15 takes about 10 hours. Heavy drinkers may clear slightly faster (0.02/hour); seniors slightly slower. Alcohol shows on breath tests below 0.01 for several hours; in urine for 12-24 hours; in hair for months.
What is one standard drink?
US standard drink = 14 grams of pure alcohol. That is 12 oz of 5% beer, 5 oz of 12% wine, or…
US standard drink = 14 grams of pure alcohol. That is 12 oz of 5% beer, 5 oz of 12% wine, or 1.5 oz of 40% spirits. UK uses 'units' = 8 g alcohol per unit (smaller). Australia uses 10 g standard drinks. Pour size at home is often larger than the standard — a 'glass of wine' is typically 6-7 oz, not 5 oz.
Can I drive after one drink?
Depends on body weight, sex, and food. A 70 kg male hits about 0.02 BAC after one standard drink — under the…
Depends on body weight, sex, and food. A 70 kg male hits about 0.02 BAC after one standard drink — under the US 0.08 limit, but above Sweden's 0.02 limit. A 50 kg female hits roughly 0.035. Practical safety advice: never drive after any alcohol if you can avoid it, and never within 3 hours of more than one drink.
Does coffee sober you up?
No. Caffeine blocks adenosine receptors and increases perceived alertness, but it does not change alcohol metabolism. You may feel less drunk while…
No. Caffeine blocks adenosine receptors and increases perceived alertness, but it does not change alcohol metabolism. You may feel less drunk while still legally impaired — a more dangerous state for driving. Only time clears alcohol. Sleep, water, and food do not speed clearance either.
Why do women get drunk faster than men?
Two reasons. (1) Body composition — women have slightly higher body fat and lower body water percentage on average, concentrating alcohol in…
Two reasons. (1) Body composition — women have slightly higher body fat and lower body water percentage on average, concentrating alcohol in less water. (2) ADH enzyme activity is lower in women's stomachs, so more alcohol reaches the bloodstream rather than being metabolised pre-absorption. The Widmark r factor (0.55 vs 0.68) captures the body water difference; the enzyme difference adds another 10-20%.
Does eating slow down alcohol absorption?
Yes — meaningfully. Food in the stomach slows gastric emptying and delays alcohol reaching the small intestine where most absorption occurs. Peak…
Yes — meaningfully. Food in the stomach slows gastric emptying and delays alcohol reaching the small intestine where most absorption occurs. Peak BAC drops by 20-50% with a substantial meal. Total alcohol absorbed is similar over the day, but the peak (and the immediate impairment) is lower. The advice 'don't drink on an empty stomach' is good — but it does not make any drinks safer for driving.