How to Calculate the Blood Alcohol Level
The blood alcohol level is a good way to find out if a person is legally drunk or if they have had too much to drink. It is a bit of a complex formula but when broken down into individual steps is fairly easy to follow and calculate. You must know the persons weight, gender and what they have been drinking to calculate this formula.
Blood alcohol level is the term used for the percentage of alcohol that is found in the blood. This percentage is used to know how much a person has been drinking in a certain amount of time. This is often used by law enforcement to find out if a person is within the legal limits of blood alcohol. Most law enforcement use a breathalyzer but there is also a formula that can be used. This formula is: %BAC = (A x 5.14/W x r) - .015 x H
- Multiply the ounces of alcohol drank by the alcohol percentage in the drink to find the liquid ounces. For example, a beer has 12 ounces and is 5 percent alcohol, so 12 times .05 is .60 liquid ounces.
- Divide 5.14 by the person's weight. For example if a person weighs 100 pounds, then divide 5.14 by 140 to get .051.
- Multiply the liquid ounces by 5.14/W and then by distribution ratio. The distribution ratio for men is .73 and women is .66. In our example assume that this is a female, so multiply .60 times .037 times .66 to get .02.
- Subtract .015. In our example .02-.015 equals .005.
- Multiply that number by the number of hours between this calculation and when the person started drinking. Say it has been 2 hours, multiply .005 times 2 to get .01.
This 100 pound female consumed one beer and two hours later will have a blood alcohol level of .01.