Blood Alcohol Content (BAC) Calculator

Estimate your blood alcohol content based on weight, gender, drinks consumed, and time elapsed. Understand impairment levels and time to sobriety.

The estimate follows the Widmark equation. Each standard drink is treated as 0.6 fluid ounces of pure ethanol, that total is scaled by 5.14 and divided by your body weight times a body-water constant, then a flat 0.015 per hour is subtracted for elimination. The constant is where the Gender selection acts: 0.73 for male, 0.66 for female, which is roughly a ten percent difference in the denominator and the reason an identical drink count reads higher for a woman of the same weight — 0.052 against 0.045 at 170 lb, three drinks and two hours. Body weight and drink count pull with roughly comparable strength here. A ten percent change to either one moves the result by about 0.007 to 0.008 at the default settings (170 lb, 3 drinks) — not the flat 0.015 in the elimination term below, a different number entirely; weight's effect is slightly asymmetric (about −0.007 for a 10 percent increase, +0.008 for a 10 percent decrease) because it sits in the denominator of a division, while drinks moves the result by a nearly symmetric ±0.0075 because it's a straight multiplication in the numerator. Hours elapsed is weaker per step but eventually decisive, since the subtraction is linear and the result is floored at zero: those three drinks at 170 lb zero out just under five hours, and every later hour still reports 0.000. Time to Sober counts forward from the already-reduced figure, not from your first drink, dividing it by the same 0.015 hourly rate. The impairment label switches at 0.02, 0.08, 0.20 and 0.30. What the formula cannot see is everything that actually varies: drinking pace, food, sex hormones, medication, liver function and how strong the pour really was. Treat it as arithmetic about averages, never as permission to drive.