how many tons of river rock do i need?
Multiply the square footage by the depth, such as 60 times 0.167 for about 10 cubic feet. When you divide the cubic feet by 27, you get the number in cubic yards. If you had 120 cubic feet, for example, divide 120 by 27 to get about 4 1/2 cubic yards. If you need the amount in tons, multiply the cubic yards by 1.35.