1 oz of Liquor (80 proof) or 40% by vol = 1 Glass of wine (6 oz) = 1 Beer (12 oz)
The human body metabolizes any of the above, on average, at a rate of 1 unit per hour. that means one beer, one glass of wine, or a drink with 1 oz of 80 proof liquor should be gone in one hour after finishing the drink. Factors that may affect the metabolizing of alcohol is the Height/weight of the person, How much you have had to eat, and foods that you have eaten, and most of all other drugs (legal, illegal, or even prescribed by a doctor) that may have been consumed. If you are drinking doubles, PGA, or doing shots with beer chashers, plan on getting someone else to drive, just to be safe.
check out erowid for more information.
Be safe, hand over the keys if you are planning to drink. better safe than sorry.