Blood Alcohol Concentration (BAC) Calculator
Estimate blood alcohol concentration using the Widmark formula. For educational purposes only — never drive if you have been drinking.
Results
What is it?
Blood Alcohol Concentration (BAC) measures the mass of alcohol per decilitre of blood (g/dL). This calculator uses the Widmark Formula, developed by Erik Widmark in the 1930s and still used in forensic toxicology. The body eliminates alcohol at approximately 0.015 g/dL per hour regardless of food, coffee, or exercise.
How to use
1. Enter the number of standard drinks consumed (1 standard drink = 14 g pure alcohol in the US). 2. Enter your body weight and select your biological sex (affects body water distribution). 3. Enter how many hours have passed since your first drink. 4. The result shows your estimated current BAC and hours remaining until sober. This is for educational purposes only. BAC varies significantly between individuals.
Example scenario
A 70 kg male who consumed 3 standard drinks over 2 hours: Alcohol = 42 g. Raw BAC = 42 / (70 x 0.68) = 0.088 g/dL. After 2 hours of elimination (0.030): BAC = 0.058 g/dL — below the 0.08 US legal limit, but still impaired.
Pro tip
The legal limit for driving in most US states is 0.08 g/dL. In many European countries it is 0.05 g/dL. Even at 0.02 g/dL, reaction time and judgment are measurably impaired. Food slows alcohol absorption but does NOT lower peak BAC — it only delays it. There is no safe way to speed up sobriety. Never drive after drinking.