BAC Calculator - Blood Alcohol Content by Weight, Sex and Time

0.15 per mille per hour - the rate your liver cannot negotiate

Your liver processes alcohol at a fixed rate of roughly 0.15 per mille per hour (0.015% BAC/h). No amount of coffee, cold showers, or "sleeping it off" changes this number. The Widmark formula - developed by Swedish chemist Erik Widmark in the 1930s - calculates blood alcohol concentration from four inputs: the grams of pure alcohol consumed, your body weight, a sex-specific distribution factor (r), and elapsed time. This calculator runs that formula and shows you a full elimination timeline.

How to calculate your BAC - step by step

Select your sex - the Widmark r factor is 0.68 for men and 0.55 for women. This reflects the difference in body water percentage.
Enter your weight in kg - alcohol dilutes across body water, so heavier people reach lower concentrations from the same drink.
Choose your drink type - beer (5%), wine (12%), spirits (40%) or enter a custom ABV percentage.
Enter the amount in ml - total volume consumed. One pint of beer = 473 ml, one glass of wine = 150 ml, one shot = 40 ml.
Enter hours since first drink - set to 0 to see peak BAC. Each hour reduces BAC by about 0.15 per mille.
Read your results - current BAC, peak BAC, grams of pure alcohol, time to full sobriety and legal limit countdowns.

Legal driving limits by country

Country / region	Limit (per mille)	Limit (% BAC)	Notes
USA (most states)	0.8	0.08%	Utah: 0.05%. Under 21: zero tolerance
UK, Canada	0.8	0.08%	Scotland: 0.05%
Germany, France, Spain	0.5	0.05%	New drivers: often 0.0 or 0.2
Australia	0.5	0.05%	Learners and P-platers: 0.0
Poland, Sweden, Norway	0.2	0.02%	Effectively zero tolerance
Czech Republic, Hungary	0.0	0.00%	Absolute zero tolerance

Real-world examples

Male, 80 kg, 2 beers (500 ml each, 5%), just finished
Pure alcohol: 39.5 g. Peak BAC: 0.73 per mille (0.073%). Time to sober: 4 h 50 min. Below US 0.08% limit but above EU 0.05%.

Female, 60 kg, 2 glasses of wine (150 ml each, 12%), 1 hour ago
Pure alcohol: 28.4 g. Peak BAC: 0.86 per mille. After 1 h: 0.71 per mille (0.071%). Above most legal limits. Sober in: ~3 h 45 min.

Male, 90 kg, 3 shots of vodka (40 ml each, 40%), 3 hours ago
Pure alcohol: 37.9 g. Peak BAC: 0.62 per mille. After 3 h: 0.17 per mille. Below 0.02% - legal in most countries.

Female, 55 kg, 1 strong beer (500 ml, 7%), just finished
Pure alcohol: 27.6 g. Peak BAC: 0.91 per mille (0.091%). Time to sober: ~6 h. One single strong beer puts a lighter woman above every legal limit.

Male, 100 kg, 1 pint of beer (473 ml, 5%), 2 hours ago
Pure alcohol: 18.7 g. Peak BAC: 0.27 per mille. After 2 h: 0.00 per mille. Fully sober. Large body weight and moderate consumption.

Common questions about blood alcohol content

What is the Widmark formula?

The Widmark formula calculates BAC as: BAC = A / (r x W) - beta x t, where A = grams of pure alcohol consumed, r = sex-specific distribution factor (0.68 male, 0.55 female), W = body weight in kg, beta = elimination rate (0.15 per mille/hour), and t = hours since drinking. The formula was published by Erik Widmark in 1932 and remains the standard for forensic BAC estimation.

Why do women reach higher BAC from the same amount of alcohol?

Two main reasons. First, women have a lower percentage of body water (52% vs 61% for men on average), so alcohol concentrates in a smaller volume. This is captured by the Widmark r factor (0.55 vs 0.68). Second, women tend to have lower levels of alcohol dehydrogenase (ADH) in the stomach lining, meaning less alcohol is broken down before reaching the bloodstream. The net result: a 60 kg woman drinking the same beer as an 80 kg man will reach roughly 60-80% higher BAC.

Can I speed up alcohol elimination?

No. Coffee, cold showers, exercise, energy drinks, charcoal - none of these speed up liver metabolism. The liver processes alcohol at 0.10-0.20 per mille per hour (average 0.15), and this rate is essentially fixed by enzyme kinetics. Eating before drinking slows absorption (lower peak BAC), but once alcohol is in the blood, only time removes it. The only proven way to lower your peak BAC is to drink less or spread consumption over more hours.

What is the difference between per mille and percent BAC?

Per mille (written as a number with the symbol) is parts per thousand. Percent BAC is parts per hundred. To convert: divide per mille by 10 to get percent. So 0.8 per mille = 0.08% BAC. The US and UK typically use percent (0.08% legal limit). Most of Europe, Australia and many other countries use per mille (0.5 per mille limit). They express the same thing in different units.

Does eating before drinking lower BAC?

Eating before drinking does not prevent alcohol absorption - it slows it down. Food in the stomach (especially fat and protein) closes the pyloric sphincter, delaying alcohol transfer to the small intestine where most absorption occurs. This means your BAC rises more slowly and peaks lower, but the total alcohol absorbed remains the same. Studies show that eating a meal before drinking can reduce peak BAC by 10-30% compared to drinking on an empty stomach.

How accurate is this calculator?

The Widmark formula is accurate to within +/- 15-20% for most people. Factors the formula does not account for: food in the stomach (slows absorption), medications (some inhibit ADH), liver health (chronic drinkers may metabolize faster), body composition (muscular people have more water than overweight people at the same weight), and drinking pattern (sipping over 4 hours vs chugging). For legal purposes, only a blood test or calibrated breathalyzer counts.

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