How is BAC calculated?

Q: How is blood alcohol content (BAC) calculated?

BAC is estimated using the Widmark formula: BAC = (Alcohol consumed in grams × 5.14) / (Body weight in pounds × r) - 0.015 × Hours since drinking. The variable 'r' is 0.73 for men and 0.66 for women, reflecting average body water differences.

Q: What is the legal BAC limit for driving?

In most US states and many countries, the legal BAC limit for driving is 0.08%. For commercial drivers it's typically 0.04%. Many countries have stricter limits: 0.05% in Australia, 0.02% in Sweden, and 0.00% (zero tolerance) in Japan for drivers under 20.

Q: How long does it take for alcohol to leave your system?

The average liver metabolizes about 0.015% BAC per hour, roughly one standard drink per hour. However, this varies based on liver health, food intake, medications, and individual metabolism. There's no way to speed up this process.

Q: Does body weight affect blood alcohol level?

Yes, significantly. A heavier person has more blood and body water to dilute the alcohol, resulting in a lower BAC for the same amount of alcohol consumed. This is why the calculator asks for body weight to provide accurate estimates.

Q: Can this calculator be used for legal purposes?

No, this calculator provides estimates only and should not be used for legal or medical decisions. Actual BAC depends on many factors including genetics, medications, food intake, and liver function. Always use a certified breathalyzer for accurate readings.

Question

How is BAC calculated?

Accepted Answer

BAC is estimated using the Widmark formula: BAC = (A × 5.14 / (W × r)) - 0.015 × H, where A is oz of alcohol, W is weight in lbs, r is gender constant (0.73 men, 0.66 women), H is hours since drinking.

🍺 Blood Alcohol Content Calculator