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Most Accurate BAC Calculator — an honest Widmark estimate
The most accurate thing any BAC calculator can do is be honest about its limits. This tool uses the Widmark formula (BAC% = alcohol ÷ (weight × r) × 100 − 0.015 × hours, r = 0.68 men / 0.55 women), but real blood alcohol is shifted materially by an empty versus full stomach, drinking pace, medications, hydration, liver health and individual metabolism — and BAC peaks after your last sip, not immediately. We show a careful estimate and state those caveats plainly rather than faking precision. The only accurate reading of your actual BAC is a breathalyzer or blood test. This is an estimate only — never use it to decide whether to drive.
Widmark: BAC% = (alcohol g / (weight g × r)) × 100 − 0.015 × hours
- r = 0.68 men / 0.55 women; elimination ≈ 0.015%/hr; US standard drink = 14 g
- Estimate only — food, meds, hydration and metabolism shift real BAC materially.
Frequently asked questions
Which BAC calculator is the most accurate?
No formula-based calculator can be exact — Widmark is an approximation used by clinicians and DUI-lawyer sites alike. The most accurate calculator is one that uses the correct equation and is honest that food, medications, hydration, pace and individual metabolism shift the real number. Only a breath or blood test measures your actual BAC.
Why does my BAC keep rising after I stop drinking?
Alcohol takes time to absorb, so BAC typically peaks 30–90 minutes after your last drink before it starts falling at about 0.015% per hour. A low reading soon after drinking can still climb, which is one reason you should never drive based on an estimate.