BAC Calculator
BAC = (Drinks × 14g × 0.789) ÷ (Weight × r) − (Hours × 0.015) where r=0.68(male) or 0.55(female)BAC=(4×14×0.789)÷(80×0.68)−(2×0.015)=44.2÷54.4−0.03≈0.051%
Free online tool
BAC Calculator
Enter your weight, gender, number of drinks and hours elapsed to estimate BAC.
Instant calculation
BAC Calculator
Enter your weight, gender, number of drinks and hours elapsed to estimate BAC.
Your result
Calculation
Your numbers stay in this browser. Nothing is uploaded or saved.
Three clear steps
How to use this calculator
- 01
Enter weight
Type your body weight in kilograms.
- 02
Select gender
Choose male (0) or female (1).
- 03
Enter drinks and hours
Type the number of standard drinks and hours spent drinking.
The formula
How this calculation works
Uses the Widmark formula. BAC decreases at approximately 0.015% per hour. This is an estimate only — do not use to determine driving fitness.
Check the method
Worked examples
Each example follows the same formula used by the calculator.
Male, 80 kg, 4 drinks in 2 hours — BAC?
BAC=(4×14×0.789)÷(80×0.68)−(2×0.015)=44.2÷54.4−0.03≈0.051%≈ 0.051% BAC (estimate only)Common questions
Questions about this calculation
What is the BAC Calculator?
The BAC Calculator helps you estimate your blood alcohol concentration based on weight, gender and drinks consumed. Enter your values and select Calculate to get an instant result.
How is the result calculated?
Uses the Widmark formula. BAC decreases at approximately 0.015% per hour. This is an estimate only — do not use to determine driving fitness.
Can you show an example?
Example: Male, 80 kg, 4 drinks in 2 hours — BAC? — ≈ 0.051% BAC (estimate only).
Is my data saved when I use the BAC Calculator?
No. All calculations run locally in your browser. Your inputs and results are never uploaded, stored or shared with anyone.
Is the BAC Calculator free to use?
Yes. The BAC Calculator is completely free. No account, sign-up or payment is required. It works on mobile, tablet and desktop.
Continue calculating