Estimate your blood alcohol content using the Widmark formula. Factors in sex, weight, drinks, time, and stomach contents with impairment levels and legal limits worldwide.
The Blood Alcohol Content (BAC) Calculator estimates your BAC using the Widmark formula, the most widely used pharmacokinetic model for alcohol absorption and elimination. It factors in your sex, body weight, number of standard drinks consumed, elapsed time, and stomach contents to provide a real-time BAC estimate.
BAC is the standard measure of alcohol intoxication, expressed as a percentage of alcohol by weight in the blood. In the United States, 0.08% is the legal driving limit for adults 21+, while many countries use lower thresholds (0.05% or even 0.02%). Even below legal limits, alcohol impairs judgment, reaction time, and coordination — the primary reasons it contributes to roughly 10,000 traffic fatalities annually in the US alone.
This calculator provides your estimated current BAC, projected time to reach legal limits, time to complete sobriety, impairment level descriptions, calorie content from alcohol, and a comprehensive table of legal limits across major countries. Remember: this is an estimate only. Individual variation in metabolism, tolerance, genetics, medications, and hydration means actual BAC may be significantly different from any calculated value.
Understanding your estimated BAC helps you make informed decisions about drinking and driving. While a calculator should never be your sole guide, it raises awareness about how quickly alcohol accumulates and how slowly it is metabolized. Keep these notes focused on your operational context. Tie the context to the calculator’s intended domain. Use this clarification to avoid ambiguous interpretation.
Widmark Formula: BAC (%) = ((Alcohol in grams × Stomach factor) / (Body weight in grams × r)) × 100 − (0.015 × hours) Where: - Alcohol grams = Number of drinks × 14g (US standard) - r = 0.68 (male) or 0.55 (female) — Widmark ratio - 0.015 = average elimination rate per hour - Stomach factor: Empty = 1.0, Partial = 0.85, Full = 0.70
Result: Peak BAC: 0.059%. Current BAC: 0.029% (after 2 hours). Time to sober: ~1.9 hours.
Three standard drinks for a 170-lb male produces a peak BAC of about 0.059% with partial stomach contents. After 2 hours of metabolism at 0.015%/hr, the current BAC drops to approximately 0.029% — below the legal limit but still mildly impaired.
Alcohol (ethanol) is absorbed primarily in the small intestine (80%) and stomach (20%). Peak blood levels occur 30-90 minutes after the last drink on an empty stomach, or 1-3 hours with food. First-pass metabolism in the stomach reduces the amount reaching the bloodstream by 10-30%. The liver metabolizes alcohol primarily via alcohol dehydrogenase (ADH) at a rate of approximately 7-10 grams per hour (roughly one standard drink).
Even at BAC levels well below 0.08%, impairment is measurable. At 0.02%, divided attention tasks suffer. At 0.04%, most people show reduced coordination and cognitive ability on standardized tests. By 0.08%, virtually everyone is significantly impaired regardless of perceived tolerance. Chronic heavy drinkers may show less behavioral impairment at a given BAC (tolerance), but their actual collision risk does not decrease — their overestimation of their own ability increases danger.
The worldwide trend is toward lower legal limits. Over 80% of countries now use limits of 0.05% or lower. Zero-tolerance laws for young or new drivers have reduced alcohol-related crashes significantly in countries that have adopted them. Several countries (including Russia, Brazil, and others) have adopted near-zero limits for all drivers with measurable reductions in traffic fatalities.
The Widmark formula is a well-validated estimate but has limitations. It assumes complete absorption and steady-state metabolism. Individual variation (genetics, CYP2E1 enzyme activity, medications, liver function) can cause actual BAC to differ by ±20% or more from calculated values.
In the US, one standard drink contains 14 grams of pure alcohol: 12 oz regular beer (5% ABV), 5 oz wine (12% ABV), or 1.5 oz distilled spirits (40% ABV/80 proof). Craft beers, cocktails, and large glasses often contain more than one standard drink.
Women typically have a higher BAC from the same consumption due to: lower body water percentage (55% vs 68%), less gastric alcohol dehydrogenase enzyme, and generally lower body weight. The Widmark r factor captures this difference (0.55 vs 0.68).
Yes significantly. A full meal before drinking can reduce peak BAC by 25-40% by slowing gastric emptying and absorption. This is why the calculator includes stomach content adjustment. However, food delays but does not prevent absorption — total alcohol consumed still matters.
No. The liver metabolizes alcohol at a relatively fixed rate (~0.015%/hr, or roughly one standard drink per hour). Coffee, cold showers, and exercise do not speed up metabolism. Only time reduces BAC. The myth of "sobering up" with coffee is dangerous — it creates a wide-awake drunk.
Many researchers and countries argue that 0.05% or lower is safer. At 0.08%, relative crash risk is approximately 4× that of a sober driver. At 0.05%, it is about 2×. The NTSB has recommended the US lower its limit to 0.05%.