⚠️ Never drive after drinking. This tool gives an estimate only — it is not a measure of whether you are safe to drive.
Free · Educational · Instant

BAC Calculator

Estimate your Blood Alcohol Content based on drinks, body weight and time — for awareness and education. This is a statistical estimate, not a substitute for judgment: the only safe choice after drinking is not to drive.

✓ Free Forever ✓ Widmark Formula ✓ Educational Use

BAC Estimator

Please enter a valid weight and number of drinks (0 or more).

Reference

What Counts as "1 Standard Drink"?

Standard drink sizes contain roughly the same amount of pure alcohol (~14 grams), even though the serving size differs.

DrinkTypical Serving~Alcohol Content
Beer330 ml (12 oz)~5% ABV
Wine150 ml (5 oz)~12% ABV
Spirits / Shot45 ml (1.5 oz)~40% ABV
Fortified Wine90 ml (3 oz)~17% ABV
The Method

How BAC Is Estimated (Widmark Formula)

This is the standard formula used in alcohol research and forensic estimation, though real BAC varies significantly by individual.

BAC % = (Alcohol consumed in grams ÷ (Body weight in grams × r)) × 100 − (0.015 × hours elapsed) r = 0.68 for men, 0.55 for women (body water distribution ratio)

Important: the Widmark formula is a population-average estimate. Actual BAC is affected by food intake, medication, genetics, drinking speed, and other factors this calculator cannot measure. Never rely on it to judge impairment.

Worked Example

Step-by-Step Example

A 70 kg male who had 3 standard drinks over 2 hours.

1
Total alcohol consumed: 3 × 14g = 42g
2
Body water distribution: 70,000g × 0.68 = 47,600g
3
Raw BAC: (42 ÷ 47,600) × 100 ≈ 0.088%
4
Subtract elimination: 0.088% − (0.015 × 2) = ≈0.058% estimated BAC
Reference — Not Advice

Legal Driving BAC Limits (Reference Only)

Legal limits vary by country and often by driver category (e.g. commercial or new drivers). These are general reference figures — always check current local law, and remember: below the legal limit does not mean unimpaired.

CountryGeneral Limit
India0.03%
USA (most states)0.08%
UK (England/Wales)0.08%
Australia0.05%
Zero-tolerance countries (e.g. some Gulf states)0.00%

Being under a legal limit does not mean it's safe to drive. Reaction time and judgment can be affected well below any legal threshold. The only fully safe BAC for driving is 0.00%.

Educational

Typical Effects by BAC Level

General ranges based on published research — individual effects vary widely.

BAC RangeTypical Effects
0.02–0.04%Mild relaxation, slight mood change
0.05–0.07%Reduced judgment, lowered inhibition, impaired coordination begins
0.08–0.10%Significantly impaired reaction time, balance and judgment
0.15%+Major impairment; risk of blackout, vomiting, loss of coordination
0.30%+Risk of alcohol poisoning — seek emergency medical help
Who Uses This

Common Reasons People Use This Tool

📚
Alcohol Education
Understand how drinks affect BAC
👥
Awareness
Plan safer, slower drinking
🎓
Health Classes
Teaching alcohol metabolism
📋
Curiosity
Understand the Widmark formula
🍽
Drink Planning
Estimate BAC before drinking
⏰
Time Tracking
Estimate alcohol elimination time
🚗
Safe Driving
Avoid driving after drinking
📈
BAC Comparison
Compare different drinking scenarios
Drink Safer

Tips for Responsible Drinking

Always Plan a Safe Ride Home

Arrange a designated driver, taxi, or ride-share before you start drinking — never decide "in the moment."

Eat Before and While Drinking

Food slows alcohol absorption, though it doesn't lower your total BAC over time.

Pace Yourself

Your body eliminates alcohol at a roughly fixed rate — drinking slower keeps your peak BAC lower.

Alternate with Water

Drinking water between alcoholic drinks helps with hydration and naturally slows your pace.

Know Your Drink Size

Different beverages contain different amounts of alcohol, so standard drink sizes matter when estimating BAC.

Remember BAC Is an Estimate

Calculator results are approximate and should never be used to decide whether it's safe to drive.

Questions

Frequently Asked Questions

No. This is a statistical estimate only. Real BAC varies with genetics, medication, food, health conditions, and more. Never use any calculator to decide whether it's safe to drive — the only safe choice after drinking is not to drive.
A formula developed in the 1930s by Erik Widmark to estimate blood alcohol concentration from the amount of alcohol consumed, body weight, gender, and time elapsed. It remains widely used as a population-average estimation method.
The formula uses a body water distribution ratio that differs by gender on average (women typically have a lower proportion of body water), which affects how concentrated alcohol becomes in the bloodstream for the same amount consumed.
The body eliminates alcohol at roughly 0.015% per hour on average, so a BAC of 0.08% takes approximately 5-6 hours to fully clear — though this varies by individual and cannot be sped up by coffee, cold showers, or exercise.
No. Only time allows your liver to metabolise alcohol. Coffee, cold showers, and exercise may make you feel more alert but do not lower your actual BAC.
Food slows how quickly alcohol is absorbed into your bloodstream, which can lower your peak BAC, but it does not reduce the total amount of alcohol your body has to process.
Not necessarily. Reaction time, judgment, and coordination can be measurably affected well below any country's legal limit. Legal limits reflect policy decisions, not a guarantee of safety.
Legal limits are set by each country's road safety policy and vary based on local research, enforcement approach, and risk tolerance — always check current local law for your location.
Yes. Body weight, gender, metabolism, food intake, medication, and overall health all affect individual BAC significantly, even with identical alcohol consumption.
Call emergency medical services immediately. Signs include confusion, vomiting, seizures, slow or irregular breathing, pale or bluish skin, and unresponsiveness. Do not leave the person alone, and keep them on their side to prevent choking.
Yes, many medications interact with alcohol and can intensify impairment even at the same BAC level, or affect how alcohol is metabolised. Consult a doctor or pharmacist about your specific medications.
No. Tolerance can reduce how impaired someone feels at a given BAC, but it does not reduce the actual BAC number or its physiological effects on reaction time and coordination.
No. This is an educational estimation tool only. Legal or medical BAC determination requires a certified breathalyzer or blood test administered by qualified personnel.
Roughly 14 grams of pure alcohol — equivalent to a 330ml beer (~5% ABV), a 150ml glass of wine (~12% ABV), or a 45ml shot of spirits (~40% ABV). See the reference table above.
No. All calculations run entirely in your browser — nothing you enter is sent to or stored on our servers.
No. Breathalyzers measure actual breath alcohol concentration directly, while this calculator provides a population-average mathematical estimate that can differ from a real device reading, sometimes significantly.
Don't drive, regardless of how you feel or what any calculator shows. Use a designated driver, taxi, ride-share service, or public transport, or simply stay where you are until you're able to travel safely the next day.

Drank Tonight? Plan a Safe Ride.

Whatever your estimate shows, the safest choice is always the same: don't drive. Book a cab, call a friend, or stay put.

🚗 No Driving ✅ Safe Ride 🔔 Ask for Help