BAC Calculator
Estimate your blood alcohol content based on the Widmark formula
Blood alcohol content (BAC) measures the amount of alcohol in your bloodstream. Even moderate drinking affects reaction time, coordination, and decision-making. Use this calculator to get a quick estimate based on the Widmark formula — the same method used in forensic toxicology worldwide. For a more personalized result that accounts for your metabolism and food intake, try the AlcoBalance app.
1 standard drink = 14g pure alcohol (355ml beer, 150ml wine, 44ml spirits)
This is an estimate only
This calculator provides a rough estimate based on the Widmark formula. Actual BAC depends on many factors including metabolism, food intake, medications, and individual physiology. Never drive or operate machinery based on a calculator estimate.
Want more accurate results?
AlcoBalance app uses your personal profile and real-time metabolism modeling for up to 30% more accurate calculations.
How the Widmark Formula Works
The Widmark formula, developed by Swedish chemist Erik Widmark in 1932, is the gold standard in forensic toxicology for estimating blood alcohol concentration. It calculates BAC using: BAC = (alcohol consumed in grams) / (body weight × distribution ratio) − (elimination rate × time). The distribution ratio (r) is 0.68 for males and 0.55 for females. The average elimination rate is 0.15‰ per hour.
Factors that affect your actual BAC include: body composition, food in stomach, hydration level, liver health, medications, and individual genetic variation in alcohol dehydrogenase enzyme activity.
Stages of Intoxication by BAC Level
The same dose affects everyone differently, but the overall picture by blood alcohol level looks like this:
Alcohol has been fully eliminated or hasn't entered the bloodstream yet.
Mild relaxation, attention drifts a little. From the outside nobody would notice.
Mood is up, you talk more, self-control drops. Reaction time is already slowing.
Coordination and speech slip. Reactions lag, and you overestimate what you can do.
Confusion, disorientation, possible memory gaps. High risk of injury.
Breathing and reflexes are suppressed. Risk of alcohol poisoning, which is a medical emergency.
How Long Until Alcohol Leaves Your System
Your liver clears alcohol at a nearly constant rate, about 0.15 ‰ per hour. Nothing speeds it up. Approximate time to full elimination for men:
| Drink | 60 kg | 80 kg | 100 kg |
|---|---|---|---|
| Beer, 500 ml (5%) | ≈ 3.5 h | ≈ 2.5 h | ≈ 2 h |
| Glass of wine, 150 ml (12%) | ≈ 2.5 h | ≈ 1.5 h | ≈ 1.5 h |
| Spirits, 50 ml (40%) | ≈ 2.5 h | ≈ 2 h | ≈ 1.5 h |
| Two beers, 500 ml each | ≈ 6.5 h | ≈ 5 h | ≈ 4 h |
| Bottle of wine, 750 ml (12%) | ≈ 11.5 h | ≈ 8.5 h | ≈ 7 h |
For women, elimination takes roughly 20–25% longer, because the distribution ratio is lower. Actual time depends on metabolism, food, and liver health. Treat these numbers as an optimistic estimate.
Frequently Asked Questions
What is permille (‰) and how does it relate to BAC percent?
Permille means one thousandth. A blood alcohol level of 0.5 ‰ equals 0.5 grams of pure alcohol per liter of blood. The US and UK write the same value as a percentage: 0.05% BAC = 0.5 ‰.
How long until alcohol is fully eliminated?
The liver processes about 0.15 ‰ per hour, roughly one standard drink. A 500 ml beer clears in about 2–3.5 hours, a bottle of wine in 7–12 hours depending on weight and sex. Details are in the table above.
What BAC does one beer produce?
A 500 ml beer at 5% contains about 20 g of pure alcohol. For an 80 kg man that's a peak of roughly 0.35–0.4 ‰; for a 60 kg woman, around 0.6 ‰. The peak arrives 30–60 minutes after the drink.
Can you speed up alcohol elimination?
No. Coffee, a cold shower, a walk, or greasy food don't make your liver work faster. It clears alcohol at a constant rate. Coffee makes you feel more alert, but your BAC stays the same. The only thing that works is time.
How accurate is an online BAC calculator?
The Widmark formula gives an estimate with an error of up to 20–30%: it ignores food, medications, hydration, and individual metabolism. Don't use it for decisions where that error matters, like whether to drive. The AlcoBalance app builds your curve from your profile and the session you're in right now, so the estimate lands closer to reality.
What is the legal BAC limit for driving?
Limits vary by country, from 0.0 to 0.8 ‰. Much of Europe uses 0.5 ‰, Scandinavia 0.2 ‰, and some countries allow no alcohol at all behind the wheel. Check your local law. Reaction time suffers well below any legal limit anyway. Safest rule: if you've been drinking, don't drive.