The weight of asphalt in tons required for a paving project may be readily calculated using a few simple tools and concepts. The weight of any substance in kilograms is related to its weight density or compactness. Weight density is the number of kilograms of a material contained in a specific volume of the material. Volume is a quantity describing how much space an object occupies, is measured in cubic metres, and depends on the dimensions of the space. One standard ton, sometimes called a short ton by engineers, is equivalent to 907 kg (2,000 lb).
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Measure the length, width and depth in cm of the space you want to fill with asphalt. For example, you may have a driveway 381 cm (150 inches) long, 254 cm (100 inches) wide and 12.7 cm (5 inches) deep.
Convert the length, width and height measurements to metres by dividing by 100, since each metre contains 100 cm. Continuing the sample exercise leads to a length of 3.81 m (12.5 feet), a width of 2.54 m (8.33 feet) and a depth of 0.127 m (0.42 feet).
Multiply the length times the width times the depth to obtain the volume in cubic metres of the space to be paved. Performing this step yields 3.81 m (12.5 feet) times 2.54 m (8.33 feet) times 0.127 m (0.42 feet) or 1.23 cubic metres (43.7 cubic feet).
Multiply the weight density of the asphalt by the volume to arrive at the weight of the asphalt needed in pounds. Consult the asphalt manufacturers if you do not know the weight density of the asphalt. In the example, use a typical weight density of 2,336.6 kg per cubic metre. Now you have 2,336.6 kg per cubic metre times 1.23 cubic metres, which equals 2,874 kg (6,336.5 lb).
Convert the asphalt weight to tons by dividing by 907 (the number of kg in a ton). Completing the sample exercise results in 2,874 kg divided by 907 kg per ton or 3.2 tons of asphalt.