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BAC Calculator (Blood Alcohol Content)
Estimate Blood Alcohol Content from drinks using the Widmark formula. See US legal driving thresholds and hours until BAC reaches 0.00.
HEALTHEstimate Blood Alcohol Content (BAC) from drinks consumed using the Widmark formula. See US legal driving thresholds (0.08% for adults 21+, 0.04% for commercial drivers, 0.02% for under 21) and hours until BAC reaches 0.00.
Widmark formula: BAC% = (alcohol_grams / (body_weight_grams × distribution_ratio)) × 100 - (0.015 × hours). Distribution ratio is 0.68 for males, 0.55 for females. One US standard drink = 14g pure alcohol (12 oz 5% beer, 5 oz 12% wine, 1.5 oz 40% spirits). Your liver clears about 0.015 BAC per hour - food, coffee, and cold showers do not speed this up.
Disclaimer: Estimate only. Actual BAC varies by metabolism, food, hydration, medications. Never drive after drinking - even a "legal" BAC impairs judgment.
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Frequently Asked Questions
How is my BAC actually calculated?
The Widmark formula: BAC% = (alcohol_grams / (body_weight_grams × distribution_ratio)) × 100 - (0.015 × hours). Distribution ratio is 0.68 for males, 0.55 for females. One US standard drink contains 14g of pure alcohol - that is 12 oz of 5% beer, 5 oz of 12% wine, or 1.5 oz of 40% spirits. The 0.015 per hour subtracts your liver's clearance rate.
What is the legal BAC limit in the US?
0.08% for adult drivers (21+) in all states except Utah, which is 0.05%. Commercial drivers (CDL) are limited to 0.04%. Drivers under 21 face a zero-tolerance limit of 0.02% in most states - effectively any detectable alcohol. Impairment starts well before 0.08%: judgment and reaction time degrade noticeably at 0.02% and crash risk doubles at 0.05%.
How long does it take to sober up?
Your liver clears about 0.015 BAC per hour, no matter what. Coffee, cold showers, food, sleep, and exercise do not speed it up. If you blow 0.10%, you will reach 0.00 in about 6.7 hours. Eating before or while drinking slows absorption but does not reduce the alcohol already in your system. The only true cure is time.
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