Online Tool Store
Blood Alcohol Estimator
Estimate blood alcohol concentration using the Widmark formula from weight, sex, drinks, and time elapsed. Educational estimate only. Runs entirely in your browser.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
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estimated blood alcohol concentration
⚠️ This is a rough estimate for education only — actual BAC varies by metabolism, food intake, and many other factors. Never use this to decide whether it's safe to drive. When in doubt, don't drive.
How it works
- Enter body weight, sex, standard drinks consumed, and hours elapsed.
- See the estimated BAC using the Widmark formula.
The formula
BAC = (alcohol grams ÷ (body weight in grams × r)) × 100 − (0.015 × hours elapsed)
r = 0.68 (male) or 0.55 (female) — Widmark's distribution ratio
FAQ
What is the Widmark formula?
A well-known approximation from 1932 that estimates blood alcohol concentration from body weight, sex (via an alcohol-distribution ratio), grams of alcohol consumed, and elimination over time. It's the basis most simple BAC calculators use, though real BAC depends on many more factors.
What counts as one "standard drink"?
About 14 grams (0.6 fl oz) of pure alcohol — roughly a 12 oz regular beer, a 5 oz glass of wine, or a 1.5 oz shot of spirits, per the commonly used US standard drink definition.
Why shouldn't I use this to decide if it's safe to drive?
This estimate ignores food intake, drinking pace, individual metabolism, medication interactions, and measurement error in "standard drinks" — real BAC can differ significantly from the estimate. The only safe choice when impairment is possible is not to drive.
Is my data uploaded anywhere?
No — every calculation happens locally in your browser. Nothing is sent to a server.
How we compare
| Feature | Online Tool Store | Manual Widmark calculation | Personal breathalyzer |
|---|---|---|---|
| Instant, no math required | ✓ | Multi-step arithmetic by hand | ✓ |
| Actually measures your body | Estimate only | Estimate only | ✓ Real measurement |
For educational understanding of the Widmark formula, this saves the arithmetic — but a real breathalyzer measurement is always more reliable than any estimate for an actual safety decision.