BAC Calculator

This applies the Widmark equation to estimate blood alcohol from the alcohol drunk, body weight, the Widmark distribution ratio r and the hours since the first drink, and it reports the estimate with the wide band those published constants imply. Individual variation is large: food, medication, body composition, sex, age, liver function, drinking pace and time all move the real figure, and the equation assumes every drink has already been absorbed, which takes 30 to 90 minutes. Only an evidential breath test or a blood test measures blood alcohol, so nothing here can tell you what a test would read or whether you are under any legal limit. The only amount of alcohol that is safe before driving is none.

Calculator Type

Weight Unit

Kilograms Pounds

Number of Drinks (kg) *

What Counts as One Drink

Body Weight (kg) *

Distribution Ratio (r)

Widmark population averages, published in litres per kilogram whichever unit you enter your weight in. They follow body water, so they fit an individual only roughly. Enter pounds if you like: they are converted to kilograms for the equation.

Hours Since the First Drink (kg) *

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Drink Size Unit

Millilitres US fluid ounces

Weight Unit

Kilograms Pounds

Size of One Drink (mL) *

Strength (% ABV) *

How Many of That Drink (mL) *

Body Weight (kg) *

Distribution Ratio (r)

Hours Since the First Drink (mL) *

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