At 70 degrees Fahrenheit, one cubic foot of water weighs approximately 62.30 pounds. Keep in mind, however, that the density of water, and thus its weight by volume, fluctuates based on its temperature. Water that is warmer than 70 F weighs less, while water that is cooler than 70 F weighs more.
According to the USGS Water Science School, a gallon of water at 70 F weighs approximately 8.33 pounds. To arrive at the weight of a cubic foot of water, multiply the weight of one gallon of water by the total number of gallons in a cubic foot, which is 7.48 gallons. The product of the two numbers, and thus the approximate weight in pounds of a cubic foot of water, is 62.30.