A sandpit is a great play area for kids of all ages. Many prefabricated sandpits are available for purchase, or it is easy to build a sandbox from basic lumber. A sandpit can hold a deceptively large amount of sand, so it is useful to calculate the volume of sand needed for the sandpit before purchasing the sand.

If the sandbox is square or rectangular, measure the length and width of the interior of the sandbox. Multiply these two numbers together, and then multiply this total by the desired depth of sand. For example, if the sandpit is 48 inches wide by 48 inches long, and a depth of 8 inches is desired, the volume of sand needed is 48x48x8=18,432 cubic inches.

If the sandbox is circular, measure the diameter of the interior of the sandbox. Divide the diameter by 2 to get the radius, square the radius and multiply it by pi (3.14). Then multiply this total by the desired depth of sand. For example, if the sandbox has a diameter of 48 inches and the desired depth of sand is 8 inches, the radius is 24 inches, and the result of the calculation is 24x24x3.14x8 =14,469 cubic inches.

Sand for sandboxes is generally purchased in quantities of cubic feet. To convert cubic inches into cubic feet, divide the amount of sand in cubic inches by 1,728. The square sandbox would require 18,432/1,728=10.7 cubic feet.