Blood Alcohol Content (BAC) Calculator

About this calculator

This calculator uses the classic Widmark formula: BAC = (A × 5.14 / (W × r)) − 0.015 × H, where A is alcohol consumed in ounces, W is body weight in pounds, r is a sex-based distribution constant (about 0.68 for men, 0.55 for women, reflecting differences in body water), and H is hours elapsed since the first drink — since the liver metabolizes alcohol at a roughly constant rate of about 0.015% per hour.

Widmark developed this in the 1930s and it's still the basis for the field-sobriety estimates used in alcohol education, and for the rough personal estimates people make before deciding whether to drive — but it's a population average, not a lab measurement: individual metabolism, food intake, and medication can shift the true value considerably, so it should never be treated as a substitute for a breathalyzer.