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What is the legal blood alcohol concentration (BAC) limit for adult drivers?

A Less than 0.08%

The legal blood alcohol concentration (BAC) limit for adults is less than 0.08%. (In Montana, the BAC limit for drivers under 21 years of age is less than 0.02%.) If your BAC is 0.08% or more, you are considered legally intoxicated and can be charged with DUI. (Note: An average 180-pound man will reach a BAC of 0.10% from the alcohol in three 1.5-ounce shots of 80-proof liquor, three 12-ounce cans of beer, or three 5-ounce glasses of wine before his body starts to break down the alcohol.) [Drinking and Driving, Chapter 6 – Physical Requirements, Montana Driver Manual]