An acre of ground contains 43,560 square feet. Consequently, a rainfall of 1 inch over 1 acre of ground could mean a total of 6,272,640 cubic inches of water. This is the equivalent of 3,630 cubic feet.
As a cubic foot of pure water weighs about 62.4 pounds, it follows that the weight of a uniform coating of 1 inch of rain over 1 acre of surface would be 226,512 pounds or about 113 short tons.The weight of 1 U.S. gallon of pure water is about 8.345 pounds. Consequently, a rainfall of 1 inch over 1acre of ground would mean 27,143 gallons of water.