100 lbs. Per cubic foot is a pretty accurate average for gravel.  That would be 20 cubic ft. Per ton.  (Nomad1 may be more accurate than myself.  Weights vary greatly depending on various factors)  If you put it down 6 inches deep, every square foot would take 0.5 cubic feet (6/12 x 1 x 1).  … Read more

27 cubic ft is one ton of gravel.. L' x W'  divide by 27 should give you a starting point for figuring out how much you need..