BAC (Blood Alcohol Content) Calculator
Free BAC calculator using the Widmark formula. Estimate blood alcohol content over time from standard drinks, weight and sex, with peak BAC, hours to zero, legal-limit thresholds and safety disclaimers. In-browser.
Loading tool...
What is BAC (Blood Alcohol Content) Calculator?
The BAC Calculator applies the Widmark formula to standard drinks, body weight and sex to estimate the peak and current blood alcohol percentage, then projects the hours until common 0.08%, 0.05% and 0.02% legal thresholds at the widely used 0.015% per hour elimination rate. It is an educational estimator with a prominent safety disclaimer — nothing here replaces a real breathalyzer, and the tool never encourages drinking and driving.
Key Benefits
- See how drinks, weight and sex shape a BAC estimate
- Watch the effect of elapsed hours on the same amount of alcohol
- Time-to-threshold table for 0.08%, 0.05% and 0.02% limits
- Clear safety messaging that this is an estimate, not a measurement
- Runs offline with nothing stored or transmitted
Common Use Cases
- •Alcohol-awareness education for students and new drivers
- •Planning a safe ride home before a night out
- •Understanding why spread-out drinking lowers the peak
- •Comparing how weight and sex change the same drink count
- •Estimating recovery time after a celebration with friends
How to Estimate Your BAC
- Count your standard drinks: Enter how many US standard drinks you have had. One standard drink contains about 14 grams of pure alcohol: a 355 ml beer, a 150 ml glass of wine, or a 44 ml shot of spirits.
- Add weight, sex and hours: Enter your body weight, sex and how many hours have passed since the first drink. The Widmark formula uses these to estimate your peak and current blood alcohol percentage.
- Read the timeline: Check when the estimate falls below 0.08%, 0.05% and 0.02%, then plan a safe ride home. Remember the result is a population average, not a personal measurement.
Key Features
- Widmark formula with male and female distribution ratios
- Peak and current BAC estimates from standard 14 g drinks
- Hours-until-zero projection at 0.015 %/hour elimination
- Time-below-threshold table for 0.08%, 0.05% and 0.02% limits
- Prominent estimates-only safety disclaimer on every screen