What is BAC (Blood Alcohol Content)?

Blood Alcohol Content (BAC) is a measure of the concentration of alcohol in the bloodstream, expressed as grams of alcohol per 100 mL of blood. A BAC of 0.08% means 0.08 grams of alcohol per 100 mL of blood. In the US, a BAC at or above 0.08% is the legal limit for driving for adults over 21. BAC is detectable in the blood 30–70 minutes after drinking and decreases at roughly 0.015% per hour on average.

What is the Widmark formula for BAC?

The Widmark formula, developed by Swedish physician Erik M.P. Widmark, estimates BAC as: BAC% = (Alcohol consumed in grams / (Body weight in grams × r)) × 100 − (Elimination rate × Time in hours). Where r is the Widmark factor (approximately 0.73 for males, 0.66 for females) reflecting different body water distribution. In US units: BAC = (A × 5.14) / (W × r) − (0.015 × H), where A = ounces of pure alcohol, W = weight in pounds, H = hours since drinking began.

How long does it take for BAC to return to zero?

The liver metabolizes alcohol at a rate of approximately 0.015% BAC per hour (about one standard drink per hour for most people). To estimate hours until sober: Hours = Current BAC / 0.015. Example: BAC of 0.12% ÷ 0.015 = 8 hours until zero. This rate is consistent regardless of coffee, cold showers, or other myths — only time reduces BAC. Individual metabolism rates vary between 0.010% and 0.020% per hour.

Why is BAC different for men and women?

Women typically reach higher BAC levels than men after consuming the same amount of alcohol, due to two main factors: (1) Body composition — women have proportionally less body water than men, so alcohol becomes more concentrated in a smaller volume of fluid. (2) Enzyme differences — women have lower levels of alcohol dehydrogenase (ADH), the enzyme that breaks down alcohol in the stomach, so more alcohol reaches the bloodstream. This is reflected in the Widmark r factor: 0.73 for males vs 0.66 for females.

What are the effects of different BAC levels?

BAC effects by level: 0.01–0.03% — subtle effects, slight mood elevation; 0.04–0.06% — relaxation, lowered inhibitions, mild impairment; 0.07–0.09% — impaired judgment and coordination, euphoria, legal limit in US at 0.08%; 0.10–0.12% — significant coordination impairment, slurred speech, delayed reactions; 0.13–0.15% — gross motor impairment, blurred vision, may feel sick; 0.16–0.19% — significant impairment, risk of blackout; 0.20%+ — confusion, stupor, risk of unconsciousness; 0.30%+ — high risk of alcohol poisoning, coma; 0.40%+ — potentially fatal.

What is the legal BAC limit for driving?

Legal BAC limits vary by country and driver type. United States: 0.08% for drivers 21+ (0.02% for under 21 in most states, 0.04% for commercial drivers). Canada: 0.08% criminal limit, 0.05% administrative (license suspension). UK: 0.08% (0.05% in Scotland). Australia: 0.05% (0.00% for learner/P-plate drivers). Germany: 0.05% (0.00% for drivers under 21 or with less than 2 years experience). Many countries have zero tolerance for any alcohol while driving.

What factors affect BAC besides drinks and weight?

Many factors affect actual BAC beyond what calculators can estimate: Food consumption (slows alcohol absorption significantly — eating before drinking can reduce peak BAC by 30–50%), drink speed (faster drinking = higher peak BAC), carbonated mixers (speed absorption), medications (many interact dangerously with alcohol), liver health (affects metabolism rate), fatigue and hydration, body composition (muscle vs fat — muscle contains more water, fat less), age (older adults metabolize alcohol more slowly), and individual genetics. BAC calculators provide estimates only.

Does coffee or food help sober up faster?

No. Nothing lowers BAC except time. Coffee makes a drunk person more alert but does not reduce BAC or impairment. Cold showers, food, and exercise do not speed up alcohol metabolism. Water rehydrates you but does not affect BAC. The liver metabolizes alcohol at a fixed rate of approximately 0.015% per hour regardless of what you eat or drink after consuming alcohol. Eating before drinking helps by slowing alcohol absorption into the bloodstream, but food eaten after drinking does not reverse absorption already complete.

🚫 NEVER DRIVE AFTER DRINKING — This calculator is for educational purposes ONLY. It cannot determine if you are safe or legal to drive.

Widmark Formula · Educational Only

BAC
Calculator

Q: What is a standard drink?

In the United States, one standard drink contains 14 grams (0.6 fluid ounces) of pure alcohol. This equals: 12 oz regular beer (5% ABV), 5 oz wine (12% ABV), or 1.5 oz (one shot) of 80-proof spirits (40% ABV). All three contain the same amount of pure alcohol despite different volumes. Many craft beers, strong wines, and cocktails contain significantly more than one standard drink.

Estimate your Blood Alcohol Content from drinks, weight, gender, and time. Understand impairment levels and how long until sober.

⚠️ Educational purposes only. BAC estimates can vary significantly from actual blood alcohol levels. Never use this to decide whether to drive. If in doubt — don't drive.

Widmark

Formula

0.08%

US Legal Limit

~1hr

Per Drink

±0.015

%/hour

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BAC Estimator

Widmark Formula — For education only

Biological Sex (affects Widmark r factor)

Body Weight

Hours Since First Drink include current hour

hrs

Drink Type

Number of Drinks

drinks

2 standard drinks · ~28g pure alcohol

Impairment Reference

BAC Levels & Impairment Effects

How blood alcohol content affects behavior, cognition, and physical ability at each level.

BAC Level	Level Name	Typical Effects	Driving Safety
0.01–0.03%	Subtle	Slight mood elevation, mild warmth. Most people feel little effect.	✅ Generally safe for most adults
0.04–0.06%	Relaxed	Relaxation, lowered inhibitions, minor impairment of reasoning, slight coordination issues.	⚠️ Beginning of impairment
0.07–0.09%	Impaired	Impaired judgment, reflexes, and coordination. Euphoria. US legal limit is 0.08%.	🚫 Illegal in US (0.08%+). Unsafe.
0.10–0.12%	Significant	Significant impairment of motor control, slurred speech, slowed reactions, emotional instability.	🚫 Seriously unsafe. High crash risk.
0.13–0.15%	Seriously Impaired	Gross motor impairment, blurred vision, possibly nauseous. Loss of balance common.	🚫 Extremely dangerous
0.16–0.19%	Very Drunk	Dysphoria (feeling bad), nausea, disorientation. Risk of blackout begins.	🚫 Cannot safely operate anything
0.20–0.25%	Stupor	Needs assistance walking. Confused, disoriented. Blackout likely.	🚫 Medical emergency risk
0.30%+	Unconscious	Loss of consciousness possible. Danger of aspiration if vomiting. Life-threatening.	☠️ Call emergency services

Legal Limits

BAC Legal Limits by Country

Legal driving limits vary significantly worldwide. Zero tolerance is increasingly common for young and commercial drivers.

Country / Region	Standard Limit	Young / New Drivers	Commercial Drivers
🇺🇸 United States	0.08%	0.00–0.02% (varies by state)	0.04%
🇨🇦 Canada	0.08%	0.00% (most provinces)	0.04%
🇬🇧 United Kingdom	0.08%	0.08% (0.05% in Scotland)	0.08%
🇩🇪 Germany	0.05%	0.00% (<21 or <2 yrs experience)	0.00%
🇫🇷 France	0.05%	0.02%	0.02%
🇦🇺 Australia	0.05%	0.00% (L/P plates)	0.00–0.02%
🇯🇵 Japan	0.03%	0.03%	0.03%
🇸🇪 Sweden	0.02%	0.02%	0.02%

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The Only Safe Choice After Drinking: Don't Drive

No BAC calculator can tell you with certainty whether you are safe to drive. Individual variation in metabolism, food intake, medications, fatigue, and genetics means two people with identical calculated BAC levels can have very different actual impairment. If you've been drinking, take a cab, rideshare, designated driver, or stay where you are. If in doubt — don't drive.

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The Widmark Formula

The Widmark formula, developed by Swedish physician Erik M.P. Widmark in the 1920s, is the forensic standard for BAC estimation. It accounts for the distribution of alcohol through the body's water content.

The r factor (Widmark factor) reflects body water content: 0.73 for males, 0.66 for females. Women have proportionally less body water and lower ADH enzyme levels, causing higher BAC from the same alcohol amount. The elimination rate of 0.015%/hour is an average — actual rates range from 0.010% to 0.020%.

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What Is a Standard Drink?

In the US, one standard drink = 14 grams (0.6 oz) of pure alcohol. This equals: 12 oz regular beer (5% ABV), 5 oz wine (12% ABV), or 1.5 oz shot of 80-proof spirits (40% ABV). All three contain identical pure alcohol despite different volumes.

Many drinks contain more than one standard drink — a 16 oz craft IPA at 8% ABV contains about 2.7 standard drinks. A large restaurant pour of wine (8 oz) at 14% is nearly 2.5 standard drinks. Always check actual serving size and ABV.

How BAC Is Calculated — The Widmark Formula

Blood Alcohol Content (BAC) is the concentration of alcohol in the bloodstream, expressed as grams of alcohol per 100 mL of blood. Our calculator uses the Widmark formula — the forensic and medical standard for BAC estimation used in legal proceedings worldwide.

Widmark Formula (US Units)

BAC% = (A × 5.14) / (W × r) − (0.015 × H) Where: A = Ounces of pure alcohol consumed = Volume (oz) × ABV% / 100 W = Body weight in pounds r = Widmark factor (male: 0.73, female: 0.66) H = Hours since drinking began 0.015 = Average BAC elimination rate per hour Pure alcohol in a drink: 12 oz beer (5% ABV) = 12 × 0.05 = 0.60 oz pure alcohol 5 oz wine (12% ABV) = 5 × 0.12 = 0.60 oz pure alcohol 1.5 oz shot (40%) = 1.5 × 0.40 = 0.60 oz pure alcohol Example: 160 lb male, 3 beers over 2 hours: A = 3 × 0.60 = 1.80 oz pure alcohol BAC = (1.80 × 5.14) / (160 × 0.73) − (0.015 × 2) BAC = 9.252 / 116.8 − 0.030 BAC = 0.0792 − 0.030 = 0.0492% ≈ 0.049% Hours to sober up: Current BAC ÷ 0.015 0.10% BAC → 0.10 ÷ 0.015 = 6.7 hours

Important Limitations

The Widmark formula provides an estimate only. Many factors affect actual BAC that this formula cannot account for: food in the stomach (slows absorption and can reduce peak BAC by up to 50%), drink speed (faster drinking raises peak BAC), carbonation in mixers (speeds absorption), medications, liver health, genetics, age, and body composition. Only a certified breathalyzer or blood test can determine actual BAC.

Frequently Asked Questions

BAC = grams of alcohol per 100 mL of blood, expressed as a %. A BAC of 0.08% means 0.08g alcohol per 100mL blood. It's detectable 30–70 minutes after drinking and decreases at ~0.015%/hour. In the US, BAC ≥ 0.08% is the legal driving limit for adults over 21. Even below 0.08%, alcohol impairs judgment, reaction time, and coordination — there is no "safe" BAC for driving.

BAC = (A × 5.14) / (W × r) − (0.015 × H). A = ounces pure alcohol consumed, W = weight in lbs, r = Widmark factor (0.73 male / 0.66 female), H = hours since drinking began. Example: 130 lb female, 2 glasses wine over 1.5 hours: A=1.2 oz, BAC = (1.2×5.14)/(130×0.66)−(0.015×1.5) = 6.168/85.8−0.0225 = 0.0719−0.0225 = 0.0494%.

Hours to sober up ≈ Current BAC ÷ 0.015. Examples: BAC 0.08% → 5.3 hours; BAC 0.15% → 10 hours; BAC 0.20% → 13.3 hours. The liver processes alcohol at a fixed rate of ~0.015%/hour regardless of coffee, water, food (eaten after), or sleep. Only time reduces BAC. Our calculator shows estimated hours-to-zero in the results.

In the US: one standard drink = 14 grams / 0.6 fl oz of pure alcohol. Equivalents: 12 oz regular beer (5%), 5 oz wine (12%), or 1.5 oz (one shot) of 80-proof spirits (40%). Many craft beers, cocktails, and restaurant wine pours contain significantly more — a 16 oz craft IPA at 8% ABV = 2.7 standard drinks. Always check actual ABV and serving size.

Two main reasons: (1) Body water — women have proportionally less body water than men, so alcohol concentrates more. (2) Enzymes — women have less alcohol dehydrogenase (ADH) enzyme in the stomach, so less alcohol is broken down before entering the bloodstream. This is why the Widmark r factor differs: 0.73 for males vs 0.66 for females. The same number of drinks will produce a higher BAC in a woman of equal weight compared to a man.

0.01–0.03%: subtle mood elevation. 0.04–0.06%: relaxation, lowered inhibitions, mild impairment. 0.07–0.09%: impaired judgment and coordination (US legal limit 0.08%). 0.10–0.12%: significant coordination loss, slurred speech. 0.13–0.15%: gross motor impairment, blurred vision. 0.16–0.20%: blackout risk. 0.20–0.30%: stupor, unconsciousness risk. 0.30%+: life-threatening alcohol poisoning. See the full effects table above.

US standard: 0.08% for drivers 21+; 0.04% for commercial drivers; 0.00–0.02% for under-21 (zero tolerance in most states). Other countries: UK 0.08% (0.05% Scotland), Canada 0.08%, Germany 0.05%, France 0.05%, Australia 0.05%, Japan 0.03%, Sweden 0.02%. Legal limits are minimums — you can be arrested for impaired driving at lower BAC if impairment is evident.

No. Nothing lowers BAC except time. Coffee makes a drunk person more awake but equally impaired ("a wide-awake drunk"). Cold showers, food eaten after drinking, exercise, and water do not reduce BAC. Eating before drinking helps by slowing alcohol absorption (can reduce peak BAC up to 50%), but food eaten after does not reverse absorption already complete. Only the liver can process alcohol, at ~0.015% per hour regardless of anything else.

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