BAC Calculator (Blood Alcohol Content)
Estimate your blood alcohol content from drinks, weight and time — compared with the 0.08% legal driving limit.
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How BAC Is Estimated
The Widmark formula: BAC% = (alcohol grams ÷ (weight in grams × r)) × 100 − 0.015 × hours, where r is 0.68 for men and 0.55 for women, and the body clears roughly 0.015% per hour. A U.S. standard drink (12 oz beer, 5 oz wine, 1.5 oz spirits) carries about 14 g of pure alcohol. The legal driving limit in every state is 0.08% (0.05% in Utah; commercial drivers 0.04%).
This is a statistical estimate — metabolism, food and medications shift real values. Whatever the number shows, if you drank, don't drive. Not legal or medical advice.
Frequently Asked Questions
How many drinks put me over 0.08%?
For a 180 lb man, roughly 4 standard drinks in an hour; for a 130 lb woman, about 2-3. Individual variation is large — treat any drinking as disqualifying for driving.
How fast does BAC drop?
About 0.015% per hour, fixed — coffee, showers and food don't speed it up. From 0.10%, sobriety takes roughly 7 hours.
Can I be arrested under 0.08%?
Yes — impairment charges (DUI/DWI) can apply at any BAC if driving is affected, and zero-tolerance laws set 0.00-0.02% for drivers under 21.
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BAC Calculator (Blood Alcohol Content)