What is a standard drink?

One standard drink contains about 14 grams of pure alcohol. This equals approximately 12 ounces of beer at 5% ABV, 5 ounces of wine at 12% ABV, or 1.5 ounces of distilled spirits at 40% ABV. Many real-world drinks contain more — craft beers (6-9% ABV), generous bar pours, and strong cocktails often equal 1.5-3 standard drinks each. Be honest about ABV and pour size when estimating.

How accurate is this BAC estimate?

Rough estimate only. Actual BAC varies significantly based on food intake (slows absorption 2-6x), hydration, medications, liver health, drinking speed, genetics (some populations have slower alcohol metabolism), age, sex, and individual variation in body water content. Two identical-weight individuals drinking the same amount can have BACs differing 30-50%. Never use a calculator to determine fitness to drive — the only safe BAC for driving is 0.00%.

At what BAC is it illegal to drive?

In the United States, the legal limit is 0.08% BAC for adults 21+ in most states. Commercial drivers (CDL): 0.04%. Drivers under 21: 0.00% (zero-tolerance laws in all states). Utah has 0.05% statewide. International limits vary: most European countries 0.05%, some Scandinavian and Eastern European countries 0.02% or 0.00%. Impairment of reaction time, judgment, and motor control begins at 0.02-0.05% — well below US legal limits.

How long does alcohol stay in my system?

Liver eliminates alcohol at approximately 0.015% BAC per hour (range 0.012-0.020 individual variation). Approximate clearance: BAC 0.08% → ~5.3 hours to zero. BAC 0.15% → ~10 hours. BAC 0.20% → ~13+ hours. Detection via specialized tests: breath test (24 hours), urine (12-48 hours, longer with ETG testing), hair (90 days). Nothing speeds up metabolism — coffee, cold showers, food, and exercise are all myths.

What are the signs of alcohol poisoning?

Alcohol poisoning is a medical emergency requiring 911. Warning signs: confusion, vomiting while semi-conscious or unconscious, seizures, slow or irregular breathing (fewer than 8 breaths/min or 10+ second pauses), hypothermia (low body temperature, bluish or pale skin), unresponsiveness. NEVER let someone "sleep it off" if these signs are present — they can die. Position on side to prevent aspiration if vomiting, call 911 immediately, stay with them until help arrives. About 2,200 people die annually in the US from alcohol poisoning.

BAC Calculator

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.

Inputs

Gender

Weight (lbs)

Standard Drinks

1 drink = 12oz beer, 5oz wine, 1.5oz liquor

Hours Since First Drink

Results

Estimated BAC

0.050%

Status

Moderate impairment

Hours Until Sober

3.4h

Impairment

Moderate — reduced coordination

BAC Over Time

Last updated: May 27, 2026Reviewed by the CalcMountain editorial team

Formula

Widmark formula for BAC estimation: BAC % = [(Alcohol consumed in grams) / (Body weight in grams × r)] × 100 − (β × hours) Where: r = Widmark factor (body water fraction) Male: 0.68 (approximate) Female: 0.55 (approximate) Higher body fat → lower r (less water for alcohol distribution) β = elimination rate ≈ 0.015% per hour (range 0.012-0.020 individual variation) Standard drink = 14 grams of pure alcohol: 12 oz beer at 5% ABV 5 oz wine at 12% ABV 1.5 oz liquor at 40% ABV (Many bar pours, craft beers, and cocktails are 1.5-3 "standard drinks") Simplified imperial formula: BAC % = [(Drinks × 14) / (Weight lbs × 454 × r)] × 100 − (0.015 × hours) = (Drinks × 0.0308 / (Weight lbs × r)) × 100 − (0.015 × hours) ≈ (Drinks × 3.08 / (Weight lbs × r)) − (0.015 × hours) Example: 170 lb male, 3 standard drinks, 2 hours since first drink. BAC = (3 × 3.08 / (170 × 0.68)) − (0.015 × 2) = (9.24 / 115.6) − 0.03 = 0.0800 − 0.030 = 0.050% (approximately) Same scenario for 140 lb female: BAC = (3 × 3.08 / (140 × 0.55)) − 0.03 = (9.24 / 77.0) − 0.03 = 0.120 − 0.03 = 0.090% (approximately) — above legal limit Time to "sober" (BAC returns to 0): Sober time hours = Current BAC / 0.015 For BAC 0.08%: 0.08 / 0.015 ≈ 5.3 hours For BAC 0.15%: 0.15 / 0.015 = 10 hours This metabolism rate (~0.015%/hour) cannot be sped up by coffee, cold showers, exercise, or food. Only time eliminates alcohol from the bloodstream. Important caveats: - Formula assumes complete absorption (peak BAC reached ~30-90 min after last drink) - Individual variation: actual BAC commonly differs from formula estimate by 20-40% - Doesn't account for food intake (delays absorption), medication interactions, or health conditions - Single ethanol "drink" varies enormously in real bars (a craft IPA at 8% ABV in a 20oz glass = ~3.5 standard drinks, not 1)

How to use this calculator

Select your sex (affects body water content estimate).
Enter weight in pounds.
Enter the number of "standard drinks" consumed (1 standard = 14g pure alcohol = 12oz 5% beer / 5oz 12% wine / 1.5oz 40% liquor). Many real-world drinks are 1.5-3x a standard drink — check ABV and pour size honestly.
Enter hours since you started drinking.
Review the BAC estimate — but understand it has high individual variation. Actual BAC could be 30-50% higher or lower than the estimate.
Use this ONLY for education about alcohol metabolism. NEVER use it to decide whether to drive — the only safe BAC for driving is 0.00%, and impairment begins well below the legal limit.
If you need to drive: arrange a ride-share, designate a sober driver, take public transit, or stay put. No calculator output justifies driving after drinking.
Approximate sober time: BAC / 0.015 = hours to return to zero. A BAC of 0.10% requires ~6.7 hours to fully metabolize. Only time works — coffee, cold showers, and food do not speed up alcohol elimination.

Worked examples

Light drinker, social setting

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%+.

Larger person, big night

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.

Rapid consumption danger

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."

When to use this calculator

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.

Common mistakes to avoid

Treating the BAC estimate as accurate enough to decide whether to drive. Don't. Individual variation is 30-50%, and impairment begins below legal limits.
Underestimating actual ethanol consumed. Bar drinks are typically 1.5-3x "standard drinks." Strong cocktails and craft beers especially. Always be honest about ABV and pour size.
Believing coffee, food, or cold showers speed up alcohol elimination. They don't. Only time works.
Combining alcohol with medications. Many medications (sedatives, opioids, sleep aids, antihistamines) amplify alcohol dangerously.
Letting someone "sleep off" alcohol poisoning. If breathing is slow/irregular, skin is bluish, person is unresponsive — call 911.
Driving after "just a few drinks." Even 0.05% BAC produces measurable impairment of judgment and reaction time. Plan rides BEFORE drinking.

Frequently Asked Questions

Sources & further reading

Alcohol and Public Health — BAC Effects — U.S. Centers for Disease Control and Prevention
Drunk Driving Statistics & Resources — U.S. National Highway Traffic Safety Administration
Alcohol Use Disorder — Treatment Resources — U.S. National Institute on Alcohol Abuse and Alcoholism

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