Measure the space to be filled with crushed rock. You need a measurement for the height, width and depth of the space to be filled with crushed rock.
Convert your measurements into the decimal equivalent of feet by dividing the inches by 12. For example: a measurement of 12 feet 1 inch is 12.08 feet.
Multiply the length by the width. Multiply that number by the depth measurement.
Divide that number by 27 to determine cubic yards needed. For example: If you total length is 200 feet, width 100 feet, with a depth measurement of 8 inches you multiply 200 times 100 times .67 divided by 27 and order 496 cubic yards.