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80 kg male, 4 drinks, 2 hours: BAC ≈ 0.073% — under the limit but impaired, and fully sober only after ~7 hours. Time is the only thing that works.
BAC math is brutal and simple: your liver eliminates about 0.015% per hour regardless of coffee, showers, or willpower. The Widmark formula estimates blood alcohol from drinks consumed, body weight, sex, and elapsed time — an estimate with ±20% individual variation, useful for understanding the timeline, never for deciding to drive. One US standard drink is 14 grams of alcohol: 12 oz of beer, 5 oz of wine, 1.5 oz of spirits.
The Widmark estimate, honest about its limits: 80 kg male, 4 drinks, 2 hours → 0.073% — and fully sober only after ~7 hours. Time is the only cure.
±20% or worse in individuals — it is the standard forensic estimate, but it cannot see your meal timing, medications, liver function, drinking pace, or genetic metabolism differences. The formula assumes average body composition (the r constant — 0.68 male, 0.55 female — is really about body water, so muscular and lean bodies run lower BAC than the estimate, higher body fat runs higher). Food in the stomach can halve peak BAC by slowing absorption, but the same total alcohol still arrives. The responsible use: understand timelines and how badly "I feel fine" correlates with legal sobriety — feeling fine at 0.08% is common precisely because alcohol impairs self-assessment first. For any driving decision, the estimate is not a defense; the only honest threshold is zero drinks.
About 0.015% BAC per hour — one standard drink per hour, roughly — and nothing accelerates it. Four drinks peaking at 0.10% needs ~7 hours to reach zero and 1.5 hours just to cross under 0.08%. This is the morning-after trap: 6 drinks ending at 1 AM can leave you at 0.05–0.06% at 8 AM — legal in some states by number, impaired by any measure, and over the limit in Utah (0.05%) and everywhere for commercial drivers (0.04%). Coffee, cold showers, exercise, and food do not speed elimination — they produce a wide-awake person with the same BAC. The liver metabolizes on its own clock, which is why the only plan that works is made before the first drink.
Three main variables. Body water: alcohol distributes into water, not fat — so at equal weight, a leaner person shows lower BAC than a higher-body-fat person, and the sex constant (0.68 vs 0.55) mostly reflects average body-water differences. Enzymes: ADH and ALDH variants change metabolism speed — the "Asian flush" ALDH2 variant causes acetaldehyde buildup, and fast metabolizers clear measurably quicker. And stomach ADH: women have less gastric alcohol dehydrogenase, so more alcohol reaches the blood unprocessed — one reason equal drinks per pound still hit harder. Tolerance is the dangerous illusion: experienced drinkers FEEL less impaired at the same BAC, but reaction time and judgment are just as compromised — tolerance masks impairment without reducing it.