BAC Calculator

The Watson formula estimates Total Body Water (TBW) from age, height, weight, and gender. BAC is then derived from TBW and the amount of pure alcohol consumed. It is more accurate than the simpler Widmark formula because it accounts for body composition differences.

This provides a reasonable estimate but actual BAC depends on additional factors such as food intake, liver health, medications, hydration level, and individual metabolism. Always err on the side of caution.

The average human body metabolizes alcohol at approximately 0.015% BAC per hour. This is a fixed rate regardless of how much you drank; your liver can only process a set amount of alcohol per hour.

Different countries set different BAC thresholds based on their traffic safety research and policy decisions. The EU generally uses 0.05%, the US and UK use 0.08%, and Japan uses a strict 0.03%. Some jurisdictions have zero tolerance for certain driver categories.

Yes, significantly. Women generally have lower Total Body Water relative to body weight, which means the same amount of alcohol produces a higher BAC. The Watson formula accounts for this biological difference.

No. This is an educational estimate only. Many factors affect your actual impairment level beyond BAC, including fatigue, medications, and tolerance. If you have consumed any alcohol, the safest option is always not to drive.

Yes, completely free with no registration required. You can use it as many times as you need with no limits or ads.

Yes. All calculations run entirely in your browser. No weight, height, age, or drinking data is sent to any server or stored anywhere.

At the average elimination rate of 0.015% per hour, a BAC of 0.08% takes roughly 5.3 hours to reach zero. A BAC of 0.15% takes approximately 10 hours. There is no way to speed up this process; coffee, cold showers, and exercise do not lower BAC.

BAC is a measurable chemical concentration in your blood. Intoxication is a subjective experience that varies by individual tolerance. A regular drinker may feel less impaired at the same BAC as an occasional drinker, but their driving ability is still reduced.