A walkthrough, end to end.
- 1
Enter the number of standard drinks consumed (a US standard drink = 14 g pure alcohol).
- 2
Enter your weight, sex, and the number of hours since your first drink.
- 3
The Widmark formula estimates BAC % minus 0.015 × hours (the average elimination rate).
Widmark formula
BAC% = (alcohol grams / (weight g × r)) × 100, minus 0.015 per hour. The distribution ratio r is approximately 0.68 for men and 0.55 for women, reflecting differences in body water composition. The formula assumes a healthy adult and average elimination — actual rates vary widely.
What you can do with this.
Standard drink reference
US standard drink = 14 g pure alcohol = 12 oz beer at 5%, 5 oz wine at 12%, or 1.5 oz spirits at 40%. Many cocktails contain 1.5–3 standard drinks; craft beer is often 1.5–2.
Why women reach higher BAC
On average, women have a lower body-water percentage than men, so the same alcohol concentrates more. The Widmark r factor (0.55 vs 0.68) captures this. Individual variation is substantial.
Why this is a rough estimate
Real BAC depends on what you ate, how fast you drank, medications, genetics (ALDH variation), liver function, hydration, and dozens of other factors. Treat the number as an educational estimate, never a permission slip.
BAC by number of drinks
For a 70 kg adult, 1 drink ≈ 0.02% BAC, 2 ≈ 0.04%, 3 ≈ 0.06%, 4 ≈ 0.08% — but only briefly, since elimination is constant. Spacing 4 drinks across 4 hours keeps peak BAC near 0.04%.
Effect of food on absorption
A full stomach slows alcohol absorption by 40–60%, lowering peak BAC and spreading it over more hours. Drinking on an empty stomach causes faster, sharper spikes — same total alcohol, more intense intoxication.
Hangover prediction
Hangover severity correlates with peak BAC — staying below 0.10% materially reduces next-day misery for most people. Hydration helps offset diuresis but doesn't speed alcohol metabolism.
Mixed drinks and craft beer
A 'martini' at a craft cocktail bar can pour 2.5–3 oz of spirits = 2 standard drinks. A 7% craft IPA in 16 oz = 1.9 standard drinks. Use the standard-drink count, not the glass count.
Spacing drinks for safer evenings
Body eliminates ~one standard drink per 90 minutes. A reasonable pace is 1 drink per hour with food and water in between — keeps BAC near 0.04% throughout the evening for most adults.
BAC calculator 2026 — what's current
Modern personal breathalyzers (BACtrack, Drager) under $100 give actual measurements within ±0.005%. Use them for self-knowledge — but the only safe BAC for driving is 0.00%.
Frequently asked.
No. Never. Even at BAC well below the legal limit, driving impairment begins. If you've been drinking, don't drive — period. Use a rideshare, taxi, or designated driver.
In the US, 0.08% for most drivers (0.04% commercial, 0.00–0.02% under 21). In most of Europe and Australia, 0.05% or lower. Many countries are at 0.02% or 0.00%.
Roughly 0.015 BAC% per hour for most adults — about one standard drink per 1.5–2 hours. There's nothing to speed it up; coffee, cold showers, and food don't help once alcohol is in your bloodstream.
Current health bodies (WHO, AHA) increasingly note that no level of alcohol is risk-free. If you choose to drink, lower is better — for cancer risk, cardiovascular health, and sleep quality.
Total alcohol is what matters — not the mix. The 'beer before liquor' folklore has no scientific basis. The risk with shots and cocktails is harder-to-track quantity.
Yes. A breathalyzer can pick up trace alcohol the morning after heavy drinking. The body eliminates ~0.015%/hour regardless of feeling sober.
No. The calculation runs entirely in your browser. Nothing is sent to a server, no analytics on inputs, no cookies. Always treat the result as educational, not actionable for driving decisions.