BAC Calculator
Calculate your Blood Alcohol Content (BAC) based on drinks consumed, body weight, gender, and time elapsed. Understand alcohol's effects and legal limits for safe decision-making.
Personal Information
Quick Presets
Alcohol Consumption
Quick Add Drinks
BAC Results
Legal Status
Impairment Effects
Time to Sober
Metabolism Info
⚠️ Important Safety Notice
- • This calculator provides estimates only - actual BAC may vary
- • Never drive under the influence of alcohol
- • Individual factors affect alcohol metabolism
- • When in doubt, don't drive - use alternative transportation
- • Seek medical attention if experiencing severe intoxication
How BAC Calculation Works
What is Blood Alcohol Content?
Blood Alcohol Content (BAC) is the percentage of alcohol in your bloodstream. It's measured as grams of alcohol per 100 milliliters of blood. BAC determines your level of intoxication and legal impairment.
Widmark Formula
This calculator uses the Widmark formula: BAC = (Alcohol consumed in grams / (Body weight in grams × r)) - (0.015 × Hours since drinking)
Where 'r' is the alcohol distribution ratio (0.73 for men, 0.66 for women)
Factors Affecting BAC
- Body Weight: Heavier people have lower BAC
- Gender: Women typically have higher BAC than men
- Food: Eating slows alcohol absorption
- Time: Alcohol metabolizes at ~0.015% per hour
- Drink Strength: Higher ABV = more alcohol
- Medications: Can affect alcohol metabolism
- Age: Older adults may have higher BAC
- Health: Liver function affects processing
How to Use This Calculator
Step-by-Step Guide
- 1. Enter your gender, weight, and age
- 2. Select the type of alcoholic beverage
- 3. Input the number of drinks consumed
- 4. Enter time elapsed since first drink
- 5. Select your food consumption level
- 6. Review your estimated BAC and impairment level
Standard Drink Definitions
- Beer: 12 oz at 5% ABV
- Wine: 5 oz at 12% ABV
- Spirits: 1.5 oz at 40% ABV
- Light Beer: 12 oz at 4% ABV
- Strong Beer: 12 oz at 7% ABV
All standard drinks contain approximately 14 grams of pure alcohol.
Example Calculation
Scenario
- Person: 180 lb male, age 30
- Drinks: 3 beers (12 oz, 5% ABV)
- Time: 2 hours since first drink
- Food: Light meal
Calculation
- 1. Total alcohol: 3 × 14g = 42g
- 2. Body weight: 180 lbs = 81,647g
- 3. Peak BAC: 42 / (81,647 × 0.73) = 0.070%
- 4. After 2 hours: 0.070 - (0.015 × 2) = 0.040%
Frequently Asked Questions
How accurate is this BAC calculator?
This calculator provides estimates based on the Widmark formula, which is widely used but not 100% accurate. Individual factors like metabolism, medications, and health conditions can significantly affect actual BAC. Always err on the side of caution.
What is the legal BAC limit for driving?
In most U.S. states, the legal limit is 0.08% for drivers 21 and over, 0.04% for commercial drivers, and 0.02% or lower for drivers under 21. However, you can be impaired and unsafe to drive at lower BAC levels.
How long does it take to sober up?
The average person metabolizes alcohol at about 0.015% BAC per hour. This means it takes about one hour to process one standard drink, but this can vary significantly between individuals.