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About This Calculator
Blood alcohol concentration estimates the percentage of alcohol in your bloodstream based on the number of drinks consumed, your body weight, sex, and time elapsed. This calculator uses the Widmark formula to approximate your BAC level and estimate when it might return to zero. It serves as an educational awareness tool and should never replace a breathalyzer or sound judgment about driving.
Quick Tips
- 1 Food slows alcohol absorption but doesn't reduce final BAC level.
- 2 Your liver clears roughly one standard drink per hour regardless of body size.
- 3 BAC of 0.05 already impairs judgment even if you feel fine.
Example Calculation
A 180 lb male drinks 4 standard beers (12 oz, 5% ABV) over 3 hours on full stomach.
Estimated BAC: 0.055% | Under legal limit (0.08%) | Time to 0.00%: ~3.7 hours
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
Your body metabolizes alcohol at a relatively constant rate of about 0.015% BAC per hour. If your BAC is 0.08%, it will take approximately 5.3 hours to reach 0.00%. No amount of coffee, water, or food can speed up this process. Only time reduces BAC.
A standard drink contains about 14 grams of pure alcohol. This equals 12 ounces of regular beer (5% alcohol), 5 ounces of wine (12% alcohol), or 1.5 ounces of distilled spirits (40% alcohol). Craft beers, strong wines, and mixed drinks may contain more than one standard drink.
Women generally have a higher BAC than men after drinking the same amount because women have a higher proportion of body fat and lower proportion of body water. Since alcohol is water-soluble, it becomes more concentrated in women's bodies. Women also produce less alcohol dehydrogenase enzyme.
No, this calculator provides estimates for educational purposes only. Actual BAC depends on many individual factors that cannot be accounted for in a formula. Never use this calculator to determine whether it is safe to drive. If you have consumed any alcohol, use a ride service or designated driver.
Eating before or while drinking slows the absorption of alcohol, resulting in a lower peak BAC. However, food does not reduce BAC once alcohol is already in your bloodstream. The same total amount of alcohol will eventually be absorbed — food just slows the process.