Consider calculating the number of tons of asphalt required for a job before making material purchases. This will allow you to buy just the amount of asphalt you need and not waste excess. The weight of material required for a driveway or walk is related to the volume of the space to be paved as well as the weight density of the asphalt. Weight density measures the compactness of a material. For example, typical asphalt has a weight density of 65.8 Kilogram per cubic foot. Volume depends on the dimensions of the space to be paved.

Measure the length and width, in inches, of the space to be paved. Also, determine the depth of asphalt desired. Typically the depth should be at least two inches. For example, say you're paving a rectangular driveway 114 inches long and 90 inches wide. Also, assume the asphalt depth will be three inches.

Convert the length, width and depth of the space to feet by dividing by 12. Continuing the example yields a length of 9.5 feet, a width of 7.5 feet and a depth of 0.25 feet.

Multiply the length by the width by the depth to obtain the volume of the space to be paved in cubic feet. Performing this step gives 9.5 feet times 7.5 feet times 0.25 feet, or a volume of 17.8 cubic feet.

Multiply the volume by the weight density of the asphalt to get the weight required in pounds. Consult the asphalt manufacturer or packaging to get the exact weight density for your specific asphalt, but for this example assume the standard weight density of 65.8 Kilogram per cubic foot. Continuing the example, you have 17.8 cubic feet times 65.8 Kilogram per cubic foot, or a weight of 1171kg.

Divide the weight by 2,000 to convert to tons, since 0.907kg. equals a ton. Completing the exercise leads to 1171kg. divided by 2,000, or about 1.3 tons of asphalt required.