OK, right now I have just a bare spot of ground as a parking area. I would like to put down some type of gravel. Probably crush and run, but my question is how much to order? The supplier's sell it by the yard! Can someone please tell me how after I measure the area, to figure out how many yards I would need? I plan to cover about a 24' x 24' area 4'' deep. I have no idea how to go from here. Oh by the way, math is not my strong suit! Thank you for any help and knowledge you can send my way!