What is Blood Alcohol Concentration?
Blood Alcohol Concentration or BAC is the amount of alcohol in the bloodstream. It is measured in percentages. For instance, having a BAC of 0.10 percent means that a person has 1 part alcohol per 1,000 parts blood in the body.
A mathematical BAC is calculated by dividing the amount of alcohol consumed by the persons total water weight. The total water weight of an individual can be derived by multiplying his or her body weight by their percent water, which differs depending on gender. Men have a higher percent of water per pound (58%) than women (49%). This strongly contributes to the generalization that men require more alcohol than women to achieve the same BAC level. Additionally, men are, on average, heavier than women. The more water a person has, the more alcohol is required to achieve the same alcohol:blood ratio, or BAC level.
- A mathematical BAC is not as accurate as a breathalyzer.
- A breathalyzer can also vary at least 15% from the actual blood alcohol concentration.
Factors that will affect the BAC in a person:
- How much alcohol you drink.
- How fast you drink.
- Body weight.
- Food in the stomach.
- The type of alcohol you drink.
- Type of mixer used.
- Temperature of the drink.
- If you are male or female.
How TrackBAC works
The TrackBAC BAC estimate is calculated using a mathematical BAC. i.e by dividing the total amount of alcohol consumed by the total amount of water in the body — effectively giving the percent alcohol per volume of water in the blood. The projected or future BAC is derived by calculating the BAC and then extrapolating forward and applying a conservative alcohol elimination factor (or rate) of .015 percent per hour. The rate of elimination in the average person is estimated from .015 to .020 percent per hour, although this can vary from person to person and in a given person from one moment to another.
Sources and further reading on BAC and alcohol: