You have to know the weight per cubic foot of the hotmix asphalt. That weight can vary greatly with the mix design. As a fairly accurate estimation it might weigh approx. 145 lbs./per cubic foot or so. Now, if you have one ton (2000 lbs) and you divide 2000 lbs by 145 lbs./cf, you would have about 13.79 cubic feet. Now you need to decide on the depth. Say 3 inches. Divide 13.79 cf by 0.25 (3 inches in feet, 3/12 in) = 55.17 sq feet div by 9 = 6.13 sq yards. So, one ton of a mix weighing 145 lbs./cf, would cover about 6.13 SY. A rule of thumb used in highway construction where I was employed for many years is: Divide the thickness (that you want to lay it at) in inches into 18. The answer is the number of sq yards that one ton will cover at the specified depth. To apply this rule to the example above, divide 3 into 18 and you get 6 sy per ton at 3 inch depth. Pretty close. If I were trying to determine how much hotmix asphalt I needed for a project and I didnt want a lot of waste, I would first find out the weight per cubic foot (compacted) from the supplier. If you do not use the compacted weight, you will either run short or your depth will be less than desired (For instance, if you want 3" depth you might need to place at 3 1/4" and the roller will compact to 3". If you just place loose at 3", you might end up with 2 3/4" depth which is 8% less thickness than designed and possibly subject to failure). Then I would measure the entire area to be paved in feet, times depth in feet = cubic feet. Then multiply the volume in cf times the weight of the mix per cf = total pounds needed. Divide by 2000 = tons need. Allow maybe upwards of 5% for waste. Note: The example weights I have used may be obsolete as I have been away from this work for a while.
