BAC Calculator

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Medical disclaimer: This calculator gives a rough estimate for informational purposes only and is not medical advice. Never drink and drive - even small amounts of alcohol impair driving. If drinking, arrange a designated driver or taxi.

Never drink and drive. This is only an estimate - impairment begins well below legal limits.

Gender

Body weight (kg)

Number of standard drinks

One standard drink = about 14 g of pure alcohol (a 330 ml beer, a 150 ml glass of wine, or a 45 ml shot of spirits).

Hours since your first drink

About BAC Calculator

What is the BAC Calculator?

The BAC Calculator is a free online tool that estimates your Blood Alcohol Content, the percentage of alcohol in your bloodstream, from the drinks you have consumed. BAC is the legal standard for intoxication worldwide: in most places, driving at 0.08 percent or above is a criminal offense, and impairment of judgment and coordination begins well below that line. Understanding your approximate BAC helps you make safer decisions before getting behind the wheel.

The calculator uses the Widmark formula, the long-established scientific method that accounts for body weight, biological sex, the number of standard drinks, and the hours since you started drinking. Alcohol distributes through body water, which is why the same drinks produce a higher BAC in smaller people and generally in women. Results appear instantly with context about typical effects at each level.

How to Use the BAC Calculator

Select your sex: Choose male or female, since body water percentage differs and changes the result.
Enter your weight: Type your body weight in kilograms or pounds.
Count your drinks: Add the number of standard drinks, where one drink is a 330 ml beer, a 150 ml glass of wine, or a 45 ml shot of spirits.
Enter the time span: Type how many hours have passed since your first drink, since the liver metabolizes about one drink per hour.
Read your estimate: Your approximate BAC appears with the legal limit comparison and expected effects.

Key Benefits

Widmark formula: Uses the established scientific equation, not guesswork.
Legal context: Compares your estimate against the common 0.08 percent driving limit.
Effects guide: Shows typical impairment at each BAC range.
Time aware: Accounts for alcohol metabolism over the drinking period.
Free with no signup: Instant, private estimates right in your browser.

Pro Tips

When in doubt, do not drive: This is an estimate, not a breathalyzer. If you feel impaired, you are impaired.
Food slows absorption: Eating before and during drinking lowers your peak BAC but does not prevent intoxication.
Standard drinks vary: Craft beers, large wine pours and cocktails often contain two or more standard drinks each.
Plan ahead: Arrange a designated driver or ride before the first drink, not after.

Frequently Asked Questions

How accurate is this estimate?

It is approximate. Real BAC varies with food, metabolism, medication and drink strength. Only a breathalyzer or blood test gives a true reading.

What is the legal driving limit?

It is 0.08 percent in most of the US and UK, 0.05 in much of Europe and Australia, and zero for new drivers in many places. Check your local law.

How long until I am sober?

The liver clears roughly one standard drink per hour. Coffee, cold air and exercise do not speed this up.

Why do women get higher BAC from the same drinks?

Women typically have a lower percentage of body water, so the same alcohol concentrates more in the blood.

Related Tools

Check body metrics with the BMI Calculator, estimate energy needs using the Calorie Calculator, and work out portions with the Percentage Calculator.

Medical Disclaimer: This calculator is for informational and educational purposes only and is not medical or legal advice. BAC estimates are approximate and cannot determine fitness to drive. Never drive after drinking. If you or someone you know struggles with alcohol, please seek professional help.

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