Blood Alcohol Content (BAC) Calculator
Estimate your Blood Alcohol Content level with our BAC calculator. Enter your weight, gender, number of drinks, and time elapsed to calculate current BAC, impairment level, and time needed to return to zero. DISCLAIMER: This calculator provides estimates only. Actual BAC varies. Never drive after drinking. Use professional testing for legal accuracy.
What is Blood Alcohol Content (BAC) and how is it measured?
Blood Alcohol Content (BAC) is the concentration of alcohol in your bloodstream, expressed as a percentage. For example, 0.08% BAC means 0.08 grams of alcohol per 100 milliliters of blood. BAC is measured via breathalyzer (estimates from breath), blood test (most accurate), or urine test (delayed reading). Factors affecting BAC: amount consumed, body weight, gender (women generally have higher BAC), drinking speed, food in stomach, and time elapsed. This calculator uses the Widmark formula for estimation.
What BAC level is considered legally drunk for driving?
Legal BAC limits vary by jurisdiction: US/Canada/UK - 0.08% for drivers 21+, 0.00-0.02% for under 21. Australia - 0.05% general, 0.00% for new drivers. Many European countries - 0.05% or 0.02%. Commercial drivers - often 0.04% or lower. At 0.08%, most people have impaired judgment, coordination, and reaction time. Effects: 0.02% = slight relaxation, 0.05% = reduced coordination, 0.08% = impaired judgment/motor skills, 0.15% = major impairment, 0.30%+ = potential loss of consciousness. Never drive after drinking - even under legal limits, alcohol impairs driving ability.
How long does it take for BAC to return to zero?
Alcohol metabolizes at approximately 0.015% BAC per hour for most people. This rate is constant - you cannot speed it up with coffee, cold showers, or exercise. Examples: 0.08% BAC takes ~5.3 hours to reach zero; 0.15% BAC takes ~10 hours. Individual metabolism varies by liver function, genetics, and regular drinking patterns. A "standard drink" (14g alcohol) takes ~1-2 hours to metabolize. The only way to sober up is time. Plan ahead: if drinking at 10 PM, you may still be impaired at 8 AM the next day.
What is a standard drink and how much alcohol does it contain?
A standard drink contains 14 grams (0.6 ounces) of pure alcohol. Examples in US: 12 oz beer (5% ABV), 5 oz wine (12% ABV), 1.5 oz distilled spirits/shot (40% ABV = 80 proof). Higher ABV means fewer ounces for a standard drink: craft beer (7% ABV) = 9 oz, fortified wine (20% ABV) = 3 oz. Many people underestimate drinks - a large wine glass or strong cocktail may be 2-3 standard drinks. Mixed drinks at bars often contain multiple shots. Always calculate based on actual alcohol content, not just number of glasses consumed.