Blood Alcohol Concentration-BAC Calculator
Estimate your BAC based on drinks consumed, weight, and time
Use this BAC Calculator to estimate your blood alcohol concentration based on weight, sex assigned at birth, standard drinks, and time since drinking began. Results are for informational purposes only and not a substitute for professional testing.
Estimated BAC
Level: 0.050%
Impairment Level
Status: Moderate
Legal Status
Driving: Likely Legal
Need to Dilute Spirits?
If you’re working with high-proof spirits, try our Alcohol Dilution Calculator to calculate the exact water needed to achieve your desired ABV.
About the BAC Calculator
The BAC Calculator estimates blood alcohol concentration using the Widmark Equation, considering body weight, sex assigned at birth, standard drinks, and time elapsed. It’s designed for educational purposes to promote responsible drinking and alcohol safety awareness.
How to Use the BAC Calculator
- Enter your body weight and select the unit (kg or lbs).
- Select your sex assigned at birth (male or female).
- Input the number of standard drinks consumed (1 standard drink = 14g of pure alcohol, e.g., 12 oz of 5% beer).
- Specify the hours since your first drink.
- Click “Calculate BAC” to view your estimated blood alcohol concentration and impairment level.
Note: This calculator uses equations based on sex assigned at birth due to limitations in current scientific data. Validated equations for trans or non-binary individuals are not available.
The Science Behind Blood Alcohol Concentration
BAC measures grams of alcohol per 100 mL of blood. The Widmark Equation estimates BAC as:
BAC = [(Dose in grams / (Body weight in grams × r)) × 100] – (0.016 × hours)
Where:
- Dose: Alcohol consumed in grams (standard drink = 14g ethanol).
- r: Distribution ratio (0.68 for males, 0.55 for females).
- 0.016: Average BAC elimination rate per hour.
Alcohol absorption takes 30-70 minutes, and BAC correlates with impairment. For details, see NHTSA’s guide on drunk driving.
Common BAC Levels
Various BAC levels indicate different impairment stages:
0.02-0.03%
Light buzz, slight relaxation
0.04-0.06%
Impaired judgment, reduced coordination
0.08%
Legal limit in many regions, significant impairment
0.10-0.12%
Severe motor impairment, slurred speech
0.20%+
High risk of blackout, severe intoxication
Frequently Asked Questions About BAC
How accurate is the BAC Calculator?
The BAC Calculator uses the Widmark Equation for reliable estimates based on weight, sex, drinks, and time. However, metabolism, food intake, and physiology may cause variations. Use certified breathalyzers or blood tests for legal or medical purposes.
What is a standard drink in the BAC Calculator?
A standard drink contains 14 grams of pure alcohol, equivalent to 12 oz of 5% beer, 5 oz of 12% wine, or 1.5 oz of 40% spirits, ensuring accurate BAC estimates.
Why does sex assigned at birth matter for BAC?
The Widmark Equation uses distribution ratios (0.68 for males, 0.55 for females) due to differences in body composition, affecting alcohol distribution and BAC estimates.
Can the BAC Calculator determine driving safety?
The BAC Calculator estimates blood alcohol concentration, but impairment varies. A BAC of 0.08% is the legal limit in many regions; however, avoid driving after drinking and arrange alternative transportation.
How does metabolism affect BAC Calculator results?
The calculator assumes a 0.016% per hour elimination rate. Individual factors like liver function, age, and food intake may cause actual BAC to differ from estimates.