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Blood Alcohol Calculator

Estimate your blood alcohol concentration with the Widmark formula: enter your drinks, body weight and drinking time — and watch your level decline over time.

100% freeNo data storedWidmark formula

A rough estimate only — not a measure of your fitness to drive

This is a pure Widmark estimate — individual values vary widely. This calculation makes NO statement about your fitness to drive and does not replace a breath or blood test. When in doubt, do not drive.

Person

kg

Drinks

How many standard drinks have you had?

Beer

0.5 L · 5%

2

Wine

0.2 L · 11%

0

Spirits

4 cl · 40%

0

Sparkling

0.1 L · 11%

0

Custom drink

ml
%
0

Time & elimination

h
‰/h

A rough estimate only — not a measure of your fitness to drive

This is a pure Widmark estimate — individual values vary widely. This calculation makes NO statement about your fitness to drive and does not replace a breath or blood test. When in doubt, do not drive.

Current blood alcohol concentration

0.39 ‰

Peak after absorption: 0.69 ‰

Pure alcohol absorbed

36.0 g

r

0.7

When are you back below …?

Estimated time remaining from now until your BAC drops below each limit.

below 0.5 ‰already below

§ 24a StVG — administrative offence from 0.5 ‰ (0.25 mg/l breath)

below 0.3 ‰in 34 min

§ 316 / § 315c StGB — criminal offence from 0.3 ‰ with impairment (relative unfitness to drive)

at 0.0 ‰in 2 h 34 min

§ 24c StVG — 0.0 ‰ during the probation period and for drivers under 21

Blood alcohol curve from first drink

Assumptions & notes

  • The basis is the Widmark formula: BAC = grams of alcohol ÷ (reduction factor r × body weight in kg). r is set to 0.7 for men and 0.6 for women — simplified average values.
  • The pure alcohol per drink is amount × ABV% × 0.8 (the density of ethanol). A 0.5 L beer at 5% therefore contains about 20 g of alcohol.
  • With the absorption deficit enabled, only around 90% of the alcohol takes effect — some is broken down in the digestive tract or never absorbed.
  • Elimination is linear at the chosen rate (default 0.15 ‰ per hour). Actual elimination varies individually between roughly 0.1 and 0.2 ‰ per hour and cannot be sped up.
  • All times are relative amounts remaining from now ("in X h Y min"), not clock times. The calculation is a rough estimate and does not replace a breath or blood test.

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Guide: Blood alcohol & the per-mille limits

The Widmark formula, Germany's limits and what the number really means

Calculating Blood Alcohol: The Widmark Formula ExplainedFeatured

Calculating Blood Alcohol: The Widmark Formula Explained

How does the Widmark formula work? Reduction factor, alcohol mass, absorption deficit and elimination rate explained step by step — with a worked example and the honest limits of the method.

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Blood Alcohol Limits in Germany: 0.0 · 0.3 · 0.5 · 1.1

Blood Alcohol Limits in Germany: 0.0 · 0.3 · 0.5 · 1.1

0.0, 0.3, 0.5 and 1.1 ‰ — what does each limit mean? Administrative offence, relative and absolute unfitness to drive, probation period and the legal basis in the StVG and StGB, clearly explained.

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Alcohol Elimination: How Long Until You're Sober Again?

Alcohol Elimination: How Long Until You're Sober Again?

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Residual Alcohol the Morning After: The Underestimated Danger

Residual Alcohol the Morning After: The Underestimated Danger

After a heavy night you are often far from sober the next morning. How to estimate how much residual alcohol is still in your blood at breakfast — and why feeling rested does not mean fit to drive.

2026-07-037 min read
Blood Alcohol on Bicycles and E-Scooters: Which Limits Apply?

Blood Alcohol on Bicycles and E-Scooters: Which Limits Apply?

1.6 ‰ absolute unfitness on a bicycle, but 0.5 and 0.3 ‰ on an e-scooter — and 0.0 during probation. Why the e-scooter is treated like a motor vehicle in law and what that means for you.

2026-07-037 min read

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Frequently Asked Questions

The calculator provides only a rough estimate based on the Widmark formula. Your actual blood alcohol level depends on many individual factors: body composition, stomach contents, drinking speed, medication, daily condition and more. Two people of the same weight can end up with markedly different values after the same drinks. This calculation makes no statement whatsoever about your fitness to drive and does not replace a breath or blood test. When in doubt, do not drive.

The Widmark formula is the classic method for estimating blood alcohol concentration (BAC). It reads: BAC in ‰ = grams of alcohol ÷ (reduction factor r × body weight in kg). The reduction factor describes the share of the body in which alcohol distributes — typically 0.7 for men and 0.6 for women. A drink's alcohol content is amount × ABV% × 0.8. The formula is named after the Swedish chemist Erik Widmark, who developed it in the 1930s.

As a rule of thumb, the body eliminates about 0.1 to 0.2 ‰ per hour, on average around 0.15 ‰. Elimination is largely constant and cannot be sped up — not by coffee, cold showers, exercise or eating. Only time lowers the level. The calculator uses 0.15 ‰ per hour by default, but you can adjust the rate between 0.10 and 0.15 ‰ to calculate more conservatively.

Not all the alcohol you drink reaches the bloodstream. Some is broken down in the gastrointestinal tract or never absorbed at all. This so-called absorption deficit is usually set at around 10%, so only about 90% of the alcohol takes effect. The calculator applies the deficit by default; you can switch it off to see the less favourable (higher) value. In forensic back-calculation the deficit is often omitted to stay on the safe side.

In Germany the administrative limit under § 24a StVG applies from 0.5 ‰ (0.25 mg/l breath alcohol). From as low as 0.3 ‰ a criminal offence for relative unfitness to drive may already exist (§ 316, § 315c StGB) if there are signs of impairment such as swerving or a crash. From 1.1 ‰ you are irrefutably deemed absolutely unfit to drive. For novice drivers in the probation period and anyone under 21, the 0.0 ‰ limit under § 24c StVG applies. Important: this calculator cannot and must not tell you whether you may drive — it is only an estimate. When in doubt, do not drive.

On average, women have a lower proportion of body water than men. Because alcohol distributes into body water, the same amount of alcohol produces a higher concentration when the distribution volume is smaller. That is why the Widmark formula uses the lower reduction factor of 0.6 for women and 0.7 for men. This is a statistical average — an individual's actual factor can differ.

No. The result is a non-binding estimate with no evidential value whatsoever. Legally, only the measured breath or blood alcohol concentration counts. The Widmark formula can over- or underestimate the true value by several tenths of a per mille. Never rely on this calculator to decide whether you can drive.

The calculator deliberately gives no clock time, but the estimated time remaining from now until your BAC mathematically drops below each limit, based on the elimination rate you set. Because elimination varies individually and the starting estimate is imprecise, you should add a generous safety margin to these times — and when in doubt, not drive at all.