Determine the number of standard drinks consumed
Convert each drink to grams of alcohol
Record the person’s body weight
Note the time elapsed since drinking began
Use the Widmark formula: BAC = (Alcohol consumed in grams / (Body weight in grams × r)) × 100 − (metabolism rate × hours)
Use r as the alcohol distribution ratio: about 0.68 for men and 0.55 for women
Use a metabolism rate of about 0.015 BAC per hour
Adjust for food intake, drink strength, and individual factors if needed
For legal or medical accuracy, use a breathalyzer or blood test