I have a question concerning estimating stone walls, and stone retaining walls. With all the different types of stone and sizes, is there a general estimating guide as to how much stone is needed for a given project? For instance, patio stone here is texas can range from 1 1/4 inch thick to 2 1/4 inch thick and can cover about 60 square feet per ton. This is easy to figure how much stone is needed, but what about when it comes to stone is various sizes for retaining walls. Here we have stone that is 2 to inches thick and of differing weight depending whether it is sandstone or limestone. So how does a person determine how much of this type of stone will cover a certain amount of the retaining wall to be built? Let's say a reatining wall or driveway entrance wall is... 4' tall 1' thick and 20' long. I know how to do the math and figure up how much the footage is, but how much stone is needed for a project like this. Thanks for any help.