The Widmark equation has estimated blood alcohol from drinks, body weight, and time since 1932. It powers most of the BAC calculators used by courts, clinics, and cautious drivers.
Your visual report appears here
Fill in the form and press Calculate. You will get your number, an interpretation chip, and a personalized chart pack drawn instantly in your browser.
- Risk spectrum with your position marked
- Reference ranges from the original publication
- Shareable link, nothing stored
Scientific references
The Swedish chemist behind the math
Erik Widmark spent the 1920s measuring how alcohol distributes through the human body and distilled his findings into a deceptively simple relationship. Alcohol spreads through body water, and body water scales with weight, so the same three drinks land very differently in a 60 kilogram person than in a 90 kilogram one. His distribution factor, about 0.68 for men and 0.55 for women, captures the different water fractions of male and female bodies. Multiply drinks by the 14 grams in a US standard drink, divide by body water mass, and you have the peak concentration.
The burn off clock
The liver clears alcohol at a nearly constant rate, roughly 0.015 percent BAC per hour for most people, regardless of coffee, cold showers, or willpower. Widmark math subtracts that steady burn off from the peak to estimate where you stand right now. Time is genuinely the only cure, which is why the hours input matters as much as the drink count.
Why your mileage varies
Food in the stomach slows absorption and lowers the peak. Certain medications and liver conditions slow clearance. Body composition shifts the distribution factor, since fat holds almost no water. Regular drinkers metabolize a bit faster than occasional ones. The estimate here is an honest average, not a guarantee, and individual readings can sit a third higher or lower.
The only safe driving number
Legal limits in the United States sit at 0.08 percent, with many countries at 0.05 or lower, but impairment measurably begins well before either line. Reaction time and lane keeping degrade from the first drink. Use this tool for curiosity, planning a safe evening, or understanding a past event. For any decision about driving, the only defensible BAC is zero.