A ton is a measurement of weight, and a cubic yard is a measurement of volume. The number of tons that a given cubic yard of material weighs depends on the material.
A cubic yard of dry building sand weighs 1.09 tons. If the cubic yard is pure water, then the answer is 0.75 ton. A cubic yard of saltwater, meanwhile, weighs 0.77 ton. Due to the anomalous expansion of water, the weight of water changes depending on the temperature. A cubic yard of ice weighs only 0.69 ton, the same as a cubic yard at of water at 45 degrees Fahrenheit.