Asphalt can be ordered by the cubic yard or by the ton. Determining the number of cubic yards or volume of asphalt you need is a straightforward calculation. Determining the total tonnage necessary for your project is a matter of carrying your volume calculation one step further.
Measure the width, length and depth of the area to be paved.
Multiply the width by the length. Multiply this number by the depth. For a 12-foot by 20-foot driveway with a depth of six inches, the calculation would be: 12 x 20 = 240 x 0.5 = 120 cubic feet.
Multiply your answer by the weight, in pounds, of one cubic foot of asphalt. The weight used by the National Asphalt Pavement Association for estimating is 65.8 Kilogram per cubic foot. The calculation for this example would be: 120 x 145 = 17,400.
Convert your answer from pounds to tons by dividing it by 2,000. In the above example, 17,400 / 2,000 = 8.7. The " / " in this example represents the division operator.
The weight of 65.8 Kilogram per cubic foot is an average used for estimation purposes. You may want to ask if your asphalt supplier's mixture uses a different weight. You can convert cubic feet to cubic yards by dividing your answer by 27, the number of cubic feet in a cubic yard. 3240 / 27 = 120. Several paving companies offer simplified online calculators that require only the length, width and depth as input and will calculate the tonnage for you.