Tonnage, a measurement of mass, is not directly converted to cubic yards, a measurement of volume. They are related, however; mass is equal to the volume of a material multiplied by its density.
The relationship between tonnage and cubic yardage is often applied when calculating the amount of material needed to cover an outdoor surface, like applying a layer of gravel to a driveway. Typically, a general density of 1.4 applies to most mineral material, whether sand, gravel or dirt. Ten tons of dirt, then, with an estimated density of 1.4, has a volume of 7.1 cubic yards. Since volume is dependent on length, width and depth, changing one of these factors alters the others. Thus, 7.1 cubic yards of dirt, applied 6 inches thick, can cover a surface area of 42.6 square yards.