What does BAC measure?

Blood Alcohol Concentration (BAC) measures the grams of alcohol present in 100 milliliters of blood. This is a standard measurement used in legal and medical contexts to determine the level of intoxication in an individual. A higher BAC indicates a higher level of alcohol in the bloodstream, which can correspond to greater impairment in motor skills and cognitive functions. The importance of accurately measuring BAC lies in its direct correlation with impairment, enabling law enforcement and legal systems to enforce laws regarding driving under the influence.

While other options touch on related concepts—such as the volume of alcohol consumed, which can influence BAC, or the time since last drink, which can help estimate BAC changes over time—they do not specifically define what BAC itself quantifies. The measurement of alcohol in breath is related to breathalyzer tests, which estimate BAC but do not measure it directly.