At your age, kiddo, any is too much. But how about for someone of legal drinking age? You may not have a BAC of 0.08% or higher if over 21. If your BAC is between 0.05% and 0.08%, you can still be convicted of a DUI if you driving was impaired. If your BAC is 0.42% or higher, congratulations: your blood would get vampires drunk.