Use the Widmark formula: BAC = (Alcohol consumed in grams ÷ (Body weight in grams × r)) × 100
Use the simplified metric form: BAC = (grams of alcohol ÷ (body weight in kg × r × 1000)) × 100
Use the alcohol amount: grams of alcohol = beverage volume in mL × alcohol by volume (ABV) × 0.789
Use r as the alcohol distribution ratio: 0.68 for men, 0.55 for women
Convert body weight to grams if needed: body weight in kg × 1000
Subtract metabolism over time: BAC decrease ≈ 0.015 per hour
Estimate current BAC: BAC after time = initial BAC − (0.015 × hours elapsed)
Use the formula for drinks in ounces: grams of alcohol = fluid ounces × ABV × 23.36
For a standard drink, use about 14 grams of pure alcohol
For a quick estimate, BAC ≈ (number of standard drinks × 14) ÷ (body weight in grams × r) × 100
Consider that food, drinking speed, medications, and individual factors affect the result
Use a breathalyzer or blood test for the most accurate measurement