On average, how long will alcohol stay in your system?

Rule of thumb. This is a surprisingly complicated question, as it turns out, in terms of physiology. To make a long story short, the rule of thumb is that it takes about one hour for the average person to clear one "standard drink" (about 1/2 an ounce of ethanol). This equates to 12 ounces of beer (3.2%), 5 ounces of wine and 1.5 ounces of whiskey.