Estimate your blood alcohol content (BAC) based on drinks consumed, body weight, gender, and time elapsed. Uses the Widmark formula to provide a rough estimate. This is for educational purposes only and should not be used to determine fitness to drive.
Blood Alcohol Content (BAC) measures the percentage of alcohol in your bloodstream — 0.08% means 0.08 grams of alcohol per 100 mL of blood. The Widmark formula, developed by Swedish chemist Erik Widmark in 1932 and refined since, provides an estimation framework that remains the foundation of forensic toxicology and DUI investigations. It accounts for the alcohol consumed, body water content (which varies by sex and body composition), and alcohol metabolism over time.
This calculator is an educational estimation tool, NOT a fitness-to-drive determination. Actual BAC depends on many factors the Widmark formula can't capture: food in your stomach (slows absorption 2-6x), hydration level, recent medication use, individual liver enzyme activity, genetic factors (some ethnicities metabolize alcohol much slower), age, sleep status, and drinking speed. Two people of identical weight and sex consuming the same drinks at the same pace can have BACs differing by 30-50%. Forensic labs use breath or blood testing for accurate measurement — not formulas.
**The only safe BAC for driving is 0.00%.** Impairment of judgment, reaction time, and motor control begins at very low BAC levels (0.02% reduces visual function and ability to perform two tasks simultaneously). Legal limits (0.08% for adults in most US states; 0.04% commercial; 0.00% under 21 in zero-tolerance states) are upper bounds for prosecution, not safety thresholds. If you're drinking and need to get somewhere, plan ride-sharing, designate a sober driver, or stay where you are. This calculator can help you understand alcohol's body chemistry but should never be used to decide whether to drive.
140 lb female, 2 glasses of wine (true 5oz pours, 12% ABV) over 2 hours. BAC estimate: (2 × 3.08 / (140 × 0.55)) − (0.015 × 2) = 0.080 − 0.030 = 0.050% Above the impairment threshold for safe driving even though below 0.08% legal limit. Judgment and reaction time meaningfully impaired. Time to clear: another ~3.3 hours. Real-world note: typical wine bar pours are 6-8 oz (not 5 oz), and house wines are often 13-14% ABV (not 12%). The "2 glasses" may actually be 3+ standard drinks, pushing BAC to 0.08-0.10%+.
200 lb male, 6 drinks (mixed beer and liquor) over 4 hours. BAC estimate: (6 × 3.08 / (200 × 0.68)) − (0.015 × 4) = 0.136 − 0.060 = 0.076% Just below 0.08% legal limit but substantially impaired. Driving is illegal in many jurisdictions even below 0.08% if officer observes impairment. Real concern: drinks at bars and home pours are typically heavy. "6 drinks" by Widmark assumes 6 × 14g pure alcohol. Actual consumption is often 1.5-2x higher. True BAC easily 0.10-0.12%. Even at the optimistic 0.076%, full clearance takes 5+ more hours. Plan an overnight stay or ride share.
160 lb female, 4 shots of liquor in 30 minutes (binge drinking). BAC estimate: (4 × 3.08 / (160 × 0.55)) − (0.015 × 0.5) = 0.140 − 0.008 = 0.132% Significant intoxication. Coordination, judgment, and emotional control substantially impaired. Vomiting, blackouts possible. BAC above 0.15% becomes dangerous; above 0.30% potentially fatal. Binge drinking (4+ drinks in 2 hours for women, 5+ for men) is the highest-risk drinking pattern. The body can't metabolize fast enough; BAC spikes faster than awareness of intoxication. Many alcohol-related deaths and assaults happen at this consumption pattern. If a person is unresponsive, breathing slowly, or has bluish skin: call 911 immediately. Alcohol poisoning is a medical emergency, not "sleeping it off."
Use this calculator for educational understanding of alcohol metabolism, planning timing around when alcohol might clear before an event requiring sobriety, or learning the relationship between body size, sex, and BAC.
DO NOT use this calculator to decide whether to drive. Period. The only safe BAC for driving is 0.00%, and any drinking before driving creates legal and safety risk.
Pair with calorie-calculator (alcohol has ~7 cal/gram — caloric impact on diet) and general health-tracking tools.
Important alcohol-related considerations:
1. **Legal limits are NOT safety limits.** US legal limit is 0.08% (0.04% commercial; 0.00% under 21 in zero-tolerance states), but impairment of judgment, reaction time, and visual processing begins at 0.02%. NHTSA crash data shows substantially elevated crash risk at 0.05% — many countries (Europe, Japan, etc.) set legal limits at 0.05% or lower for this reason.
2. **Individual variation is enormous.** The Widmark formula assumes "average" metabolism. Genetic variants (ALDH2 deficiency common in East Asian populations), liver health, medications, hormonal state, recent eating, and sleep all affect BAC. Two identical-weight people drinking identical amounts can have BACs differing 40%+.
3. **Drinks at bars aren't "standard drinks."** Standard = 14g alcohol = 12 oz 5% beer / 5 oz 12% wine / 1.5 oz 40% liquor. Real-world: craft beers (6-9% ABV), generous bar pours (8+ oz wine, 2+ oz liquor shots), strong cocktails (Long Island Iced Tea ≈ 4 standard drinks). Be honest about actual ethanol consumed.
4. **Alcohol metabolism cannot be sped up.** Coffee, cold showers, exercise, food (eaten AFTER drinking), and "remedies" do not eliminate alcohol faster. Liver processes ~one standard drink per hour. Only time clears alcohol.
5. **Combining alcohol with medications can be dangerous.** Sedatives, opioids, antihistamines, sleep aids, and many other medications dramatically amplify alcohol effects, often life-threateningly. Read medication warnings.
6. **Plan transportation BEFORE drinking.** Make the decision sober. Use ride-share apps, designate a sober driver, or stay put. The cost of an Uber is trivially small compared to DUI ($10,000+ legal costs + license + insurance impact for 7+ years), crash injury, or worse.
7. **Recognize alcohol poisoning.** Unresponsiveness, vomiting while semi-conscious, slow/irregular breathing, low body temperature, or bluish skin = medical emergency. Call 911. Don't let someone "sleep it off."
8. **Long-term health.** Heavy drinking causes liver damage, increases cancer risk (breast, colon, liver, esophagus), raises blood pressure, impairs cognition, and contributes to mental health problems. CDC moderate drinking definition: up to 1 drink/day for women, 2 for men — but the safest amount for many health outcomes is zero.
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1 drink = 12oz beer, 5oz wine, 1.5oz liquor
Estimated BAC
0.050%
Status
Moderate impairment
Hours Until Sober
3.4h
Impairment
Moderate — reduced coordination