Blood Alcohol Content is a measurement of alcohol intoxication used for legal or medical purposes. A BAC of 0.10 (0.10% or one tenth of one percent) means that there are 0.10 g of alcohol for every 100 ml of blood which is the same as 21.7 mmol/l. A BAC of 0.0 is sober, while in the United States 0.08 is legally intoxicated, & above that is very impaired. BAC levels above 0.40 are potentially fatal