That depends on a lot of things. Typically though, a concentration of 4 "normal" measures (5 ounces of wine, 12 ounces of beer) will take about 30 minutes to "peak" in your bloodstream and then clear your system in the next 2 hours after that. The rate at which it clears your system is constant, though, so 2 measures will take twice as long and so on. It has been know for people who have had 4 pints of English beer to still be too drunk to drive a car after a break of 8 hours and a lot of sleep.
