Blood Alcohol Concentration (“BAC”) is the amount of alcohol present in a person's bloodstream. In legal matters, a BAC can be used to verify an individual’s alcohol impairment.

A person's BAC is determined by several factors including the number of drinks consumed, the type of drink consumed, the body weight of the drinker, and the amount of time that has elapsed since the first drink was consumed.

To calculate a person's BAC, follow the directions below:

1) Count the total number of drinks consumed. One drink is equivalent to...
- one ounce of 100-proof liquor; or
- one 5-ounce glass of table wine; or
- one 12-ounce bottle of regular beer

2) Using the chart below, find the box where the number of drinks corresponds to the body weight of the person. The number in the box is the percent of blood alcohol produced after drinking.
(For example: 120 lbs. and 5 drinks = 0.156% .)

3) Calculate the percent of alcohol removed from the body since the first drink consumed. This value is obtained by multiplying the number of hours elapsed by 0.015%.
(For example: 6 hours x 0.015% = 0.09% .)

4) Subtract the result of Step #3 from the result of Step #2. This is the final BAC percentage.

[Created from NHTSA chart, with modifications]