Blood Alcohol Calculator
Estimate your blood alcohol level by the Widmark formula from sex, weight and drinks, with grams of alcohol, time to sober up and the 0.0/0.5/1.1 ‰ limits.
Drinks
Note: These calculations are for informational purposes only and do not replace professional tax or financial advice. All information without guarantee.
FAQ
Frequently Asked Questions
How is blood alcohol content calculated?
BAC is calculated using the Widmark formula: alcohol in grams divided by (body weight times reduction factor – 0.68 for men, 0.55 for women). The result is blood alcohol in per mille. The calculator also deducts a 10 % absorption deficit; the body then breaks down about 0.1-0.15 per mille per hour.
What are the legal alcohol limits for driving in Germany?
From 0.5 per mille driving is an administrative offence (§ 24a StVG): for a first offence 500 euros, a 1-month driving ban and 2 points. From 0.3 per mille it is already a criminal offence if there are alcohol-related failures or an accident (relative unfitness to drive, § 316 or § 315c StGB). From 1.1 per mille it is always a criminal offence (absolute unfitness to drive). Drivers in their probationary period and under 21 must stay at 0.0 per mille (§ 24c StVG: 250 euros, 1 point).
Does the calculator take into account how long ago I was drinking?
No. The calculator shows the peak value you would reach if all the alcohol entered were absorbed at once (minus a 10 % absorption deficit, without any breakdown so far) and counts down from there at 0.15 or 0.1 per mille per hour. Example: a man weighing 80 kg drinks two 0.5 l beers at 5% – that is 40 g of alcohol, 36 g of it in the blood, 36 / (80 × 0.68) = 0.66 per mille and a breakdown time of about 4 h 25 min to 6 h 37 min. It cannot reliably tell you whether you are fit to drive again, because the actual value can differ considerably depending on drinking duration, food and metabolism.
Guide
What is the Blood Alcohol Calculator?
The blood alcohol calculator estimates blood alcohol content after consuming alcoholic drinks and the expected time to sober up.
How does the Blood Alcohol Calculator work?
Enter sex, weight and drinks consumed. The calculator computes blood alcohol using the Widmark formula: BAC = alcohol amount x 0.9 / (body weight x distribution factor), i.e. minus a 10 % absorption deficit. The hourly breakdown of 0.1-0.15 per mille gives a time range until the value is back at 0.0.
Key Data and Facts
Widmark factor: men 0.68, women 0.55. Absorption deficit: 10 %. Alcohol metabolism: approx. 0.1-0.15 per mille/hour. Limits: 0.0 per mille in the probationary period and under 21 (§ 24c StVG), from 0.3 per mille punishable with signs of impairment, from 0.5 per mille administrative offence (§ 24a StVG: 500 euros, 1-month driving ban, 2 points), from 1.1 per mille absolute unfitness to drive.
Step-by-Step Guide
How to calculate your blood alcohol level step by step: 1. Enter sex and body weight: The Widmark distribution factor is 0.68 for men and 0.55 for women. 2. Enter the drinks: Specify the type, quantity and alcohol content. Pure alcohol (g) = quantity (ml) x alcohol content (vol-%) x 0.8 / 100. Example: 0.5 l of beer (5 %) = 500 x 0.05 x 0.8 = 20 g of alcohol. 3. Calculate the per-mille value: Per mille = alcohol (g) / (body weight x distribution factor). 4. Subtract the absorption deficit: About 10-30 % of the alcohol never reaches the blood. The calculator cautiously deducts 10 %. 5. Calculate the breakdown time: The body breaks down about 0.1-0.15 per mille per hour. The calculator shows both values (per-mille value / 0.15 and per-mille value / 0.1) – plan with the longer one. 6. Note the limits: 0.0 per mille in the probationary period and under 21, from 0.3 per mille a criminal offence with signs of impairment, from 0.5 per mille an administrative offence, from 1.1 per mille absolute unfitness to drive. The calculator is no basis for deciding whether you drive.
Calculation Example
Man, 80 kg, drinks 2 x 0.5 l beer (5 %): alcohol = 2 x 20 g = 40 g, minus 10 % absorption deficit = 36 g. Per mille = 36 / (80 x 0.68) = 36 / 54.4 = approx. 0.66 per mille. Breakdown to 0.0 per mille: 0.66 / 0.15 = approx. 4 h 25 min to 0.66 / 0.1 = approx. 6 h 37 min.
Sources
Official sources
Calculations are based on applicable German laws and official data:
Full methodology at Methodology.
Reviewed by Konstantin Iakovlev · Last updated:
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