According to Aware Awake Alive, a nonprofit dedicated to educating people on the dangers and symptoms of alcohol overdoses, BAC represents the percent of your blood that is concentrated with alcohol. A BAC of 0.10 means that 0.10 percent of your bloodstream is composed of alcohol.
Want to check what your BAC might be after a night out? Aware Awake Alive has an alcohol tracker on its website. According to the tracker, a 140-pound person reaches the legal intoxication level for most states, 0.080, after three drinks.