About this site and how it calculates
PromilleCheck is a small independent site that does one thing: it estimates blood alcohol content and says plainly how little that estimate is worth for deciding whether to drive. There is no company behind it and nothing is sold here.
The formula
Every figure on this site comes from one tested module. The arithmetic is the Widmark equation, published by Erik Widmark in 1932, which is still the basis of forensic alcohol calculation:
A is the grams of pure alcohol consumed, W is body mass in kilograms, t is hours since the first drink, r is the Widmark distribution factor and β the elimination rate.
The constants and where they come from
The density of ethanol, 0.789 g/ml at 20 °C, is a physical constant (CRC Handbook of Chemistry and Physics). The average distribution factors of 0.68 for men and 0.55 for women are the values used in forensic practice (Widmark 1932; Seidl, Jensen and Alt, International Journal of Legal Medicine 114, 2000, pages 71–77). The elimination rate of 0.15 ‰ per hour is the figure German and Nordic road-safety authorities use for an average adult; individual rates run roughly from 0.10 to 0.20.
Switching on height and age replaces the average factor with one worked out from your own body, using the total-body-water equations of Watson and colleagues (American Journal of Clinical Nutrition 33, 1980, pages 27–39) divided by the water fraction of whole blood, 0.80. Published versions of the male age coefficient differ in the third decimal place; at age 40 the disagreement is about 0.14 litres out of some 42, far inside the equation's own standard deviation of 3.76 litres, so it does not move any digit you see.
How the legal limits were checked
Every limit on the legal limits page was read off that country's own government source — the statute, the official legal database or the national authority — not off a news article or another comparison site. Each entry carries the link and the date it was checked. Two figures that circulate widely are deliberately not presented as law: Germany's 1.1 ‰ threshold comes from settled court practice rather than from the wording of § 316 of the criminal code, and the United States has no single federal figure for drivers under 21 because each state sets its own.
If you find a figure that is out of date or wrong, the Report a wrong result link under the calculator fills an email with the page and the inputs so the case can be redone by hand.
What this site is not
It is not medical advice, it is not legal advice, and it is not evidence of anything. It cannot tell you that you are fit to drive, and it will never tell you how much you can drink and still drive. The only level that is safe behind the wheel is 0.00.
BAC = A / (r × W) − β × t
- r = 0.68 (Man) / 0.55 (Woman)
- β = 0.15 ‰/h
- A = ml × % vol ÷ 100 × 0.789 g/ml · 1 US standard drink = 14 g
Checked against the official source on October 23, 2026