BAC Calculator
Calculate your estimated Blood Alcohol Content.
Alcohol Consumption
BAC Estimate
Enter consumption details to calculate BAC
About This Calculator
The BAC (Blood Alcohol Content) Calculator helps you estimate your blood alcohol concentration based on the amount of alcohol consumed, your weight, gender, and time elapsed. BAC is expressed as a percentage of alcohol in your bloodstream.
This calculator uses the Widmark formula, which accounts for alcohol distribution and elimination. It provides estimates only - actual BAC can vary based on many factors including metabolism, food consumption, medication, and individual differences. Never drive after drinking.
Formula & Calculation Method
BAC Calculation (Widmark Formula):
Total Alcohol (oz) = Number of Drinks × Drink Size (oz) × Alcohol Content (%)
Alcohol (grams) = Total Alcohol (oz) × 28.3495
Weight (grams) = Weight (lbs) × 453.592
Initial BAC = [Alcohol (g) ÷ (Weight (g) × r)] × 100
r = 0.68 (men) or 0.55 (women)
BAC after time = Initial BAC - (Elimination Rate × Hours)
Elimination Rate = 0.015% per hour (average)
The Widmark formula accounts for alcohol distribution (r factor) and elimination. Women typically have lower r values due to lower water content and different body composition. Alcohol is eliminated at approximately 0.015% per hour, though this varies by individual.
How to Use This Calculator
- Enter Weight: Input your body weight in kilograms.
- Select Gender: Choose your biological sex (affects alcohol distribution).
- Enter Drinks: Input number of drinks consumed.
- Enter Drink Size: Input size of each drink in fluid ounces.
- Enter Alcohol Content: Input alcohol by volume (ABV) percentage.
- Enter Time: Input hours since first drink.
- View Results: See estimated BAC, legal status, and time to reach zero BAC.
Frequently Asked Questions
What is a safe BAC level?
There is no "safe" BAC for driving. In most US states, 0.08% is the legal limit, but impairment begins at much lower levels (0.02-0.03%). The safest approach is to not drive after consuming any alcohol.
How accurate is the BAC calculator?
The calculator provides estimates based on average metabolism. Actual BAC can vary significantly based on food consumption, metabolism rate, medication, hydration, and individual factors. It should not be used to determine if you're safe to drive.
How long does it take for alcohol to leave your system?
Alcohol is eliminated at approximately 0.015% BAC per hour on average. However, this varies by individual. It can take several hours for BAC to reach zero, and you should never drive until completely sober.
Can I speed up alcohol elimination?
No. Coffee, cold showers, exercise, and other methods do not speed up alcohol elimination. Only time can reduce BAC. The liver processes alcohol at a relatively constant rate of about one standard drink per hour.
Expert Reviewed
This calculator was reviewed by NumCalculators Editorial Team, Multi-disciplinary Expert Team