Determine the amount of alcohol consumed in grams
Determine body weight in kilograms or pounds
Use the Widmark formula: BAC = (Alcohol in grams / (Body weight in grams × r)) × 100
Use r = 0.68 for men and r = 0.55 for women
If using pounds, use: BAC = (A × 5.14 / (W × r)) – 0.015 × H
In the pounds formula, A = ounces of alcohol consumed
In the pounds formula, W = body weight in pounds
In the pounds formula, H = hours since drinking started
Convert drinks to ounces of pure alcohol if needed
Use 0.6 oz of pure alcohol per standard drink
Subtract alcohol metabolism over time using 0.015 BAC per hour
Compare the result to legal or clinical BAC thresholds if needed