BAC Calculator

How BAC Estimation Works

This calculator provides a rough estimate of blood alcohol content (BAC) using the Widmark formula. It is for educational purposes only.

The Widmark formula

BAC = [(Drinks × 14g) ÷ (Weight in grams × r)] × 100 − (0.015 × Hours)

Where r = 0.68 for males, 0.55 for females (body water ratio). The 0.015 factor represents the average rate at which the body metabolizes alcohol per hour.

Step-by-step

1. Enter the number of standard drinks (1 drink = 14g pure alcohol = one 12oz beer at 5% or one 5oz wine at 12%).
2. Enter your weight in pounds.
3. Select biological sex (affects the r coefficient).
4. Enter hours since your first drink.

Worked example

3 drinks, 180 lb male, 2 hours since first drink. Estimated BAC ≈ 0.056%. This is below the 0.08% legal limit in most US states but still impairs judgment.

Important warning

This is a rough estimate. Real BAC varies with metabolism, food intake, medication, fatigue, and many other factors. Never use this calculator to decide if you are safe to drive. If you have been drinking, do not drive.