In most states, what is the per se blood alcohol concentration (BAC) limit for drivers age 21 and older?

In every US state, the per se blood alcohol concentration limit for drivers age 21 and older is 0.08%, except in Utah, which lowered it to 0.05% in 2018. A BAC at or above the limit is itself a violation regardless of how impaired you appear — 'per se' means the BAC alone proves the offense. Drivers under 21 face stricter limits (zero tolerance to 0.02% depending on state) because the legal drinking age is 21. Commercial drivers face a 0.04% limit when operating a commercial vehicle. Note that impairment begins well below the legal limit: most drivers show measurable degradation in driving ability at BACs as low as 0.02%. The legal limit is the threshold at which you are presumed too drunk to drive; you can be charged with impaired driving below the limit if your driving demonstrates impairment.