*** Warning ***
There is no blood alcohol calculator that is 100% accurate because of the number of factors that come into play regarding the consumption and reduction (burn off) rates of different people. Factors include the sex (male/female) of the drinker, differing metabolism rates, various health issues and the combination of medications that might be taken, drinking frequency, amount of food in the stomach and small intestine and when it was eaten, elapsed time, and others. The best that can be done is a rough estimation of the BAC level based on known inputs.

This is in no way purported to be a guideline for how much you can drink and still drive or avoid being arrested!!!!!!
The best policy is DON'T DRINK and DRIVE! Period.

The basic formula for estimating blood-alcohol concentration is available from The National Highway Traffic Safety Administration.