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BAC Calculator
Estimate blood alcohol content from drinks, weight, sex and time — an estimate only.
1 drink = 12 oz beer / 5 oz wine / 1.5 oz spirits
Estimated BAC
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Blood alcohol content.
| US legal status | — |
|---|---|
| Impairment | — |
| Hours to sober | — |
| Drinks | — |
Show our math
Enter your figures above to see the step-by-step working.
Estimate only — never drive after drinkingEverything computed client-side — nothing leaves this page
How the BAC Calculator Works
Blood alcohol content estimates the percentage of alcohol in your bloodstream. This calculator uses the Widmark formula: the alcohol you drank (each standard drink is about 0.6 fl oz of pure alcohol) spread through your body water — which depends on weight and sex — minus roughly 0.015 per hour as your liver processes it.
It is only an estimate. Real BAC depends on food, hydration, medications, metabolism and drink strength, and it can keep rising after your last drink. In the US, 0.08 is the legal driving limit, but impairment starts well below that. The only safe amount before driving is none.
BAC = (alcohol oz × 5.14 ÷ (weight × r)) − 0.015 × hours
Warning: a rough estimate only — never use it to decide whether to drive. If you have been drinking, do not drive.
Frequently Asked Questions
How is BAC estimated?
With the Widmark formula, from the alcohol consumed, your body weight and sex, minus about 0.015 per hour for metabolism. It’s an estimate, not a measurement.
What is a standard drink?
About 0.6 fl oz of pure alcohol — roughly a 12 oz beer, 5 oz of wine, or 1.5 oz of spirits.
Can I use this to decide if I can drive?
No. It’s only an estimate and real BAC varies with many factors. Impairment begins below the legal limit, so never drive after drinking.
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