Blood Alcohol Content Calculator

Estimate your blood alcohol concentration based on alcohol consumption, body weight, gender, and time elapsed. This calculator provides an estimate only and should not be used to determine if it's safe to drive.

Number of Standard Drinks One standard drink equals 14g of pure alcohol (12oz beer, 5oz wine, or 1.5oz liquor)

Body Weight Enter your body weight

Weight Unit

Biological Sex Different body compositions affect alcohol metabolism

Hours Since First Drink How many hours have passed since you started drinking

Hours Since Last Drink How many hours have passed since your last drink

Quick Examples:

How to Use This Calculator

Enter the number of standard drinks you've consumed
Input your body weight and select the appropriate unit
Select your biological sex, as this affects alcohol metabolism
Enter the time elapsed since your first and last drink
Click Calculate to see your estimated blood alcohol content

Formula Used

BAC = (Alcohol Consumed × 5.14 / Body Weight × r) - 0.015 × Hours

Where:

Alcohol Consumed = Total ounces of alcohol consumed
5.14 = Average alcohol distribution ratio
Body Weight = Your body weight in pounds
r = Gender constant (0.73 for males, 0.66 for females)
0.015 = Average alcohol elimination rate per hour
Hours = Hours since drinking began

Example Calculation

Real-World Scenario:

A 180-pound male has consumed 3 standard drinks over 2 hours.

Given:

Number of drinks = 3
Body weight = 180 pounds
Gender = Male (r = 0.73)
Hours since first drink = 2

Calculation:

BAC = (3 × 5.14 / 180 × 0.73) - 0.015 × 2

BAC = (15.42 / 131.4) - 0.03

BAC = 0.117 - 0.03

Result: 0.087% BAC (above the legal driving limit of 0.08% in most states)

Why This Calculation Matters

Practical Applications

Understanding personal alcohol tolerance
Making informed decisions about driving
Monitoring alcohol consumption for health

Key Benefits

Preventing DUI/DWI offenses
Reducing alcohol-related health risks
Promoting responsible drinking habits

Common Mistakes & Tips

Many people underestimate the size of their drinks. A "large" beer may contain 2-3 standard drinks, and cocktails often contain multiple servings of alcohol. Be accurate about your consumption to get a realistic BAC estimate.

Coffee, cold showers, or exercise do not speed up alcohol metabolism. Only time allows your body to process alcohol. The average person eliminates alcohol at a rate of about 0.015% BAC per hour, regardless of what they consume or do.

Eating before or while drinking can slow alcohol absorption, potentially resulting in a lower peak BAC. This calculator provides estimates based on average conditions and doesn't account for food consumption, which can affect your actual BAC.

Frequently Asked Questions

In all 50 U.S. states, the legal limit for drivers 21 and older is 0.08% BAC. For commercial drivers, the limit is 0.04%. For drivers under 21, any detectable amount of alcohol is illegal (zero tolerance laws).

Alcohol is metabolized at an average rate of about 0.015% BAC per hour. This means it takes approximately one hour to metabolize one standard drink. However, this can vary based on individual factors like liver health, metabolism, and other variables.

No. This calculator provides only an estimate of your BAC. Individual metabolism rates, health conditions, medications, and other factors can affect your actual BAC. The only safe approach is to not drive after consuming any alcohol.

References & Disclaimer

Medical Disclaimer

This blood alcohol content calculator is for informational purposes only and should not be used to determine if it is safe to drive or perform other tasks. The actual effects of alcohol on an individual can vary significantly based on numerous factors not accounted for in this calculator. Always drink responsibly and never drink and drive.

References

National Institute on Alcohol Abuse and Alcoholism - Alcohol Facts and Statistics
Centers for Disease Control and Prevention - Moderate Drinking
National Highway Traffic Safety Administration - Drunk Driving

Accuracy Notice

This calculator uses the Widmark Formula, which provides an estimate of blood alcohol content. Individual factors such as metabolism rate, health conditions, medications, and other variables can affect your actual BAC. This calculator should not be used for legal purposes or to determine fitness to drive. The results are estimates only and may not reflect your actual blood alcohol content.

About the Author

Kumaravel Madhavan

Web developer and data researcher creating accurate, easy-to-use calculators across health, finance, education, and construction and more. Works with subject-matter experts to ensure formulas meet trusted standards like WHO, NIH, and ISO.

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health other-health-lifestyle blood alcohol content medical fitness body

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