Free BAC Calculator Online
Blood Alcohol Content by drink type with legal limits, time-to-sober chart and safety tips
Blood Alcohol Content (BAC) is the concentration of alcohol in your bloodstream, expressed as a percentage. This calculator estimates your BAC based on the number and type of drinks, your body weight, sex, and time since drinking — and shows you how long until you reach legal driving limits and full sobriety.
Frequently Asked Questions
About the BAC Calculator
The Widmark formula, developed by Swedish scientist Erik Widmark in the 1920s, remains the foundation of BAC estimation in forensic science and medicine. It uses a volume of distribution factor (r) that differs between males and females because women generally have proportionally less body water — causing alcohol to be more concentrated in their bloodstream at the same intake.
BAC affects different people differently depending on tolerance, food intake, hydration, genetics, and medications. This calculator provides estimates based on population averages — individual BAC can vary by ±30% from these figures.
Even at BAC levels below legal driving limits, reaction time and judgment are measurably impaired from the very first drink. The "legal limit" defines criminal liability, not the threshold of impairment. The only reliable way to sober up is time — coffee, food, and water do not accelerate alcohol metabolism.
Formula Used
BAC = (Alcohol grams / (Body weight × r)) - (0.015 × Hours)
r = 0.68 for men, 0.55 for women
When Should You Use This?
The BAC Calculator is ideally suited for fitness enthusiasts, healthcare professionals, and individuals monitoring their health who need to perform quick, accurate calculations related to general calculations. Use this tool when you need to verify figures, compare different scenarios, or get a precise answer without manual computation errors.
What Does The Result Mean?
The calculated metrics provide a scientifically validated baseline for your health or fitness goals. While these numbers are highly accurate based on standard medical formulas, they should serve as a guide rather than a replacement for professional medical advice.
Example Calculation
BAC estimate for a 70 kg man after 3 beers in 2 hours
📥 Inputs
- Sex: Male
- Body weight: 70 kg
- Drinks: 3 standard beers (355 ml, 5% ABV each)
- Time elapsed: 2 hours
🔢 Calculation Steps
- 1Alcohol in each beer: 355 ml × 0.05 × 0.789 g/ml = 14.0 g per beer
- 2Total alcohol: 3 × 14.0 = 42.0 g
- 3Distribution factor (r) for men = 0.68
- 4Widmark formula (peak BAC): 42.0 / (70,000 g × 0.68) = 0.000883 = 0.088%
- 5Subtract elimination: 0.015% × 2 hours = 0.030%
- 6Estimated BAC after 2 hours: 0.088% − 0.030% = 0.058%
Limitations of this Calculator
- Formulas are based on population averages and may not perfectly reflect individuals with extreme muscle mass or atypical body compositions.
- Does not replace a physical examination or clinical diagnosis by a certified medical professional.
- Calculations cannot account for underlying metabolic conditions or genetic factors that influence individual health metrics.
How to Use the BAC Calculator
- 1Enter your values into the BAC Calculator input fields above.
- 2Review the input labels to ensure you are using the correct units.
- 3Click the "Calculate" button to get your instant result.
- 4Use the step-by-step breakdown to understand how the result was calculated.
- 5Export or copy your result to use in reports or share with others.
Tips & Best Practices
- Your liver clears ~0.015% BAC per hour. A BAC of 0.08% takes 5-6 hours to clear.
- Double-check your input units before calculating — using the wrong unit is the most common source of errors.
- Bookmark this BAC Calculator for quick access next time you need it.
- Use the share button to send your results to a colleague or save them for later reference.
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⚠️ Health Disclaimer: Results provided by this calculator are for informational and educational purposes only. They do not constitute medical advice. Always consult a qualified healthcare professional, doctor, or registered dietitian before making any health, fitness, or dietary decisions.