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Know Your LimitsKnow Your Rights Before You Drink and Drive  
It's never a good idea nor a safe idea to drink and drive. But if you
do, you'd better know your limits. The Blood Alcohol Calculator (BAC)
to the right will calculate an approximation of your blood alcohol level based
on your weight and the number of drinks you've had (if you're a woman,
your BAC will be higher). If your level is greater than 0.05, you could
be arrested for DWAI.

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Blood alcohol content (BAC) can be calculated with simple information such as a person’s weight, gender, and the amount of alcohol consumed in a given period. The most common formula for calculating BAC in this way is known as the Widmark formula. The amount of alcohol in a drink can vary widely; this article will use examples drawing upon the standard drink size in the United States.
Find your formula. The simplified version of the Widmark formula is: BAC = [Alcohol consumed in grams / (Body weight in grams x r)] x 100. In this formula, "r" is the gender constant: r = 0.55 for females and 0.68 for males.
Count the number of drinks. In order to calculate BAC using the Widmark formula, you will need to count how many drinks have been consumed in a given period. To be as precise as possible, the number of drinks counted should be based on a standard drink size and alcohol content, rather than the number of glasses, bottles, etc. consumed. This is because the volume and content of drinks vary widely. The standard drink size varies from country to country and from drink to drink. In the United States:
Find the alcohol dose. Once you have the number of standard drinks consumed, multiply that number by 14 to derive the alcohol dose in grams. This will give you the alcohol dose—the amount of alcohol consumed.
Take your body weight in grams and multiply it by the gender constant. The gender constant is 0.55 for females and 0.68 for males. If you know your body weight in pounds but not in grams, use one of the following formulas:
Divide the alcohol consumed in grams by (body weight in grams x gender constant.). This step will give you a raw number based on the alcohol content in your body.
Multiply the raw number by 100. Taking the raw number in the step above and multiplying it by 100 will give you your BAC as a percentage.
Account for elapsed time. If you have been drinking over a period of time, you will need to account for the elapsed time and the amount of alcohol that your body has already metabolized by the time you calculate your BAC. To do this, use the following formula:
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