Multiply the length (L), in feet, by the width (W), in feet, by the height (H), in feet, and divide by 27. This number is how many cubic yards of crushed stone you need. As an example, let's say your DIY project is a patio, and it calls for the use of crushed stone as a base. If your patio is 20 feet long and 10 feet wide, and you need 6 inches ...