How much asphalt do you need? A 40 by 12 foot driveway takes about 10.7 tons, built the ordinary way as a 2 inch base course with a 1.5 inch surface course over it. That is 6.1 tons of base and 4.6 tons of surface, and the reason it comes out as two numbers rather than one is that a driveway is paved in two passes with two different mixes.
Asphalt is sold by weight because the plant weighs the truck, but it is specified by thickness and quoted by the square yard. Getting from one to the other is a single line of arithmetic, run once for each course.
How much asphalt you need, worked once per course
Tonnage of one course
tons = area × thickness ÷ 12 × density ÷ 2,000
Area in square feet, thickness in inches, density in pounds per cubic foot
On that 40 by 12 driveway, which is 480 square feet:
- Base course at 2 inches: 480 × 2 ÷ 12 = 80 cubic feet
- Surface course at 1.5 inches: 480 × 1.5 ÷ 12 = 60 cubic feet
- Together, 140 cubic feet, plus a 5 percent allowance, is 147 cubic feet
- At 145 pounds per cubic foot that is 21,315 pounds, or 10.66 tons
Split back out, the base course is 6.09 tons and the surface course 4.57. The surface is 43 percent of the tonnage on this driveway and a larger share of the bill, because the finer surface mix costs more per ton than the coarse base.
What a ton of asphalt actually covers
At 145 pounds per cubic foot, a ton is 13.8 cubic feet of compacted material. How far that goes depends entirely on how thick you lay it:
- At 1.5 inches, one ton covers about 110 square feet
- At 2 inches, about 83 square feet, which is a little over 9 square yards
- At 3 inches, about 55 square feet
The highway version of the same fact is a factor rather than a density: the Indiana DOT design manual puts compacted mixtures at 110 pounds per square yard per inch, so a ton laid 2 inches thick covers 9.1 square yards. That is within about one percent of the figure above, and the gap is only the difference between 145 and 146.7 pounds per cubic foot.
Order five percent over, not ten
Ten percent is the standard allowance for gravel, concrete and almost everything else on this site, and asphalt is the exception. Hot mix arrives at around 300 degrees with the clock running. It cannot be returned, it cannot be stored, and what is left over cools into a lump in the back of the truck. The allowance is not insurance, it is a purchase.
On this driveway the difference between 5 and 10 percent is about half a ton, which at a typical plant price is real money for material that goes to waste. Five percent covers the thin spots and what stays in the barrow.
Ask the plant about the minimum load
Small jobs do not scale down the way the arithmetic suggests. A plant that will not send a truck out for less than a few tons turns a 3 ton job into a 5 ton invoice, and the delivery charge is the same either way. Ask what the minimum is before you finalise the size, because on a small driveway it can be cheaper to widen the job than to pay for asphalt you do not lay.
Blacktop, asphalt, hot mix
They are the same material. Blacktop is the older domestic name, hot mix asphalt or HMA is what the plant and the specification call it, and asphalt on its own is what most people type. If a contractor quotes blacktop and a supplier quotes HMA, nobody is selling you anything different.
Work out your own driveway
Frequently asked
A 20 by 20 foot driveway is 400 square feet, which at a 2 inch base course and a 1.5 inch surface course takes about 8.9 tons with a 5 percent allowance. Widen or lengthen it and the tonnage moves in direct proportion.
About 83 square feet laid 2 inches thick, or 110 square feet at 1.5 inches. A ton is 13.8 cubic feet of compacted material at 145 pounds per cubic foot, so the coverage depends entirely on the thickness.
Yes. Blacktop, asphalt and hot mix asphalt are three names for the same paving material, and which one you hear depends on the region and on whether you are talking to a contractor or a plant.