Multiply the number of tons of asphalt by 2,000 to convert to a weight in pounds. For example, 4.2 tons of asphalt results in 4.2 tons times 2,000 lb. per ton, or a weight of 8,400 lb.
Divide the asphalt weight by its weight density, in pounds per cubic foot, to arrive coverage volume in cubic feet. Performing this step leads to 8,400 lb. divided by 145 lb. per cubic foot, or a volume of 57.9 cubic feet.
Divide the volume by 27 to convert to cubic yards, because a single cubic yards equals 27 cubic feet. Completing the example, you have 57.9 cubic feet divided by 27 cubic feet per cubic yard, or a coverage volume of 2.1 cubic yards.