BAC Calculator
Estimate your blood alcohol concentration (BAC) and time to sober using the Widmark formula. Free online BAC calculator.
Weight in:
Body Weight
kg
Gender
Number of Drinks
drinks
Drink Type
Hours Since First Drink
hrs
Your Estimated BAC Is
—
Safe
How is BAC Calculated?
Blood Alcohol Concentration (BAC) estimates the percentage of alcohol in your bloodstream. This calculator uses the Widmark formula:
The Widmark factor is 0.68 for males and 0.55 for females (reflecting average body water content). The elimination rate is 0.015 per hour, which is the average rate at which the body processes alcohol.
Example
A 70 kg male who drinks two beers and waits one hour has a BAC of about (28 ÷ (70000 × 0.68)) − (0.015 × 1) ≈ 0.044. This is below the 0.08 legal limit but above the 0.05 caution threshold, so he should not drive.
Common Use Cases
- Estimating whether you may be over the legal driving limit.
- Understanding how body weight, gender, and time affect alcohol processing.
- Planning safe celebrations by estimating time until sober.
FAQs
What is the legal BAC limit for driving?
In most U.S. states the legal driving limit is 0.08%. For commercial drivers it is typically 0.04%, and for drivers under 21 it is often 0.00–0.02%. Always check your local laws.
Does this calculator guarantee I am sober to drive?
No. BAC estimates are based on averages and can vary with metabolism, food, medications, and drink strength. When in doubt, do not drive.
Can coffee or a cold shower lower my BAC?
No. Only time lowers BAC. Coffee, water, and showers may make you feel more alert but do not speed up alcohol elimination.