Confidence votes 27. you should drink at least 7 to 10 average sized glasses of water each day. One average sized glass is about eight ounces. There are 16 ounces in a pint, 2 pints in a quart, and 4 quarts in a gallon, so, mathematically, there are about 128 ounces in a gallon. If the eight ounces is divided by the 128 ounces, then the average person drinks roughly 0.625 gallons of water per day.