Asphalt Paving Calculations

Surface Area

• Simple paving jobs require relatively few surface calculations, but larger or oddly shaped areas are more difficult. Complex areas should be divided into simple shapes to make area calculations easier. Practically any surface can be divided into a combination of squares, circles, rectangles and triangles. Areas of squares and rectangles are calculated by multiplying length and width. The area of triangular sections is one half of their length times width. The area of a circular region is calculated by squaring its radius then multiplying that number by 3.14.

Volume

• By itself, the area calculation has little value for determining how much asphalt is needed to cover an area. To find the total volume of material required, the area of each section must be multiplied by the desired thickness. Most asphalt pavement is measured in inches, so this number must be converted into feet. Divide the number of inches by 12 to find the thickness in feet, then multiply this number by the surface area to find the total volume of asphalt required.

Weight

• Weight calculations are separate from volume calculations due to the difference in density between types of paving materials. There is no practical way to calculate the density of certain materials, so it is necessary to find this number from information supplied by the supplier or manufacturer. Multiply the density value, which is measured in pounds per cubic foot, by the calculated volume to find the total weight of the asphalt in pounds. This number can be converted into tons by dividing it by 2,000.

Cooling Time

• Determining how long it takes for freshly paved asphalt to cool is critical for making last-minute adjustments and fixes before the material sets. Once the asphalt cools, it is nearly impossible to smooth it and fill any remaining gaps without tearing up paved material. The calculation for cooling time is a complex equation that requires measurements of wind speed, ambient temperature and asphalt thickness. The National Asphalt Pavement Association provides free access to a mix cooling time calculation tool on their website.