As of 2015, over-the-counter breathalyzer test kits can measure blood alcohol concentration and are accurate in determining impairment. These test kits can be found at pharmacies, department stores, gas stations and online retailers.
BAC can also be estimated by online calculators that take into consideration factors such as age, gender, rate of consumption, drink strength, body/type, fat/muscle content, metabolism, emotional state, medications, food, carbonation, medical conditions such as diabetes and alcohol intolerance, but these results are highly subjective and unreliable.
DMV.org states that all 50 states have now set .08 percent BAC as the legal limit for driving under the influence (DUI) or driving while impaired (DWI). For commercial drivers, the legal limit is .04 percent and there is a zero tolerance policy for anyone under the age of 21.