How the Blood Alcohol Calculator Works
This calculator estimates your blood alcohol content (BAC) using the Widmark formula, an established method for BAC estimation. It helps you check whether your estimated level is within legal driving limits.
The Widmark Formula
BAC = grams of alcohol / (body weight x C)
Where the coefficient C varies by sex and stomach condition:
| Condition | Male | Female |
|---|---|---|
| Empty stomach | C = 0.7 | C = 0.5 |
| Full stomach | C = 1.2 | C = 0.9 |
Grams of alcohol = ml of beverage x ABV/100 x 0.789 (density of ethyl alcohol).
Why a Full Stomach Makes a Difference
On a full stomach, food slows gastric emptying and thus alcohol absorption into the blood. The higher C coefficient with a full stomach produces a lower BAC. Important: food does not reduce the total amount of alcohol absorbed, but lowers the peak concentration.
Alcohol Elimination
The liver eliminates alcohol at a constant rate of approximately 0.15 g/l per hour, regardless of any popular remedy. Coffee, cold showers, exercise, food: nothing accelerates the process. The only variable is time.
Important Warnings
BAC values are estimates. Actual BAC depends on individual factors: absorption speed, liver metabolic efficiency, medication use, hydration, and health conditions. This calculator DOES NOT replace a certified breathalyzer. When in doubt, the safest choice is always not to drive.