BAC Calculator

Estimate your blood alcohol content based on the number of drinks consumed, your weight, sex, and time elapsed.

One standard drink = 12 oz beer, 5 oz wine, or 1.5 oz spirits.

Your body weight in pounds.

Biological sex affects alcohol metabolism rate.

Time elapsed since your first drink.

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What is Blood Alcohol Content?

Blood Alcohol Content (BAC) measures the percentage of alcohol in your bloodstream. A BAC of 0.08% means 0.08 grams of alcohol per 100 milliliters of blood. In all 50 US states, a BAC of 0.08% or higher is legally impaired for driving. Effects begin at much lower levels.

How BAC is Calculated

BAC is estimated using the Widmark formula: BAC = (alcohol consumed in grams / (body weight in grams × gender constant)) - (metabolism rate × hours). The gender constant is 0.68 for men and 0.55 for women. The body metabolizes approximately 0.015% BAC per hour regardless of body size.

BAC Levels and Their Effects

At 0.02-0.03% BAC, you may feel slightly relaxed. At 0.05-0.06%, judgment and inhibitions are reduced. At 0.08%, legal impairment begins with poor coordination and reaction time. At 0.15%, significant impairment occurs. At 0.30%+, there is risk of loss of consciousness. At 0.40%+, there is risk of death.

Factors Affecting BAC

Beyond weight and sex, BAC is affected by food in the stomach (food slows absorption), rate of drinking (faster drinking = higher peak BAC), medication interactions, fatigue, hydration level, and individual metabolic differences. This calculator provides estimates — actual BAC may vary.

Frequently Asked Questions