There are a number of ways to test an individuals BAC. The most common method used by law enforcement officers is the breath testing device, which measures the alcohol level in the breath from the lungs. BAC can also be determined by drawing blood and measuring the amount of alcohol in the blood itself.
Blood alcohol concentration is directly correlated with the degree of impairment an individual displays when driving after drinking. Although an individual may not exhibit gross signs of inebriation, he/she is nevertheless impaired, even at a BAC level lower than that allowed by most state laws.
Only 17 states and the District of Columbia have set the legal BAC limit at .08. However, studies show that the relative risk of being killed in a single vehicle crash for drivers with a BAC level between .05 and .09 is 11 times that of drivers with .00 BAC level. At the .08 level, all drivers, even experienced ones, show impairment in driving ability. As BAC increases, the degree of impairment also rises dramatically.
There is no formula to determine BAC solely from the amount of alcoholic beverages consumed. BAC levels vary from person to person, and can vary within an individual on a case-by-case basis.
An individuals BAC depends upon that persons gender, weight, metabolism, time period over which the alcohol was consumed and the amount of food in the stomach prior to drinking. Although a persons BAC can be estimated, the level cannot be determined solely by the number of drinks consumed, and cannot be precisely calculated by a persons height and weight.