Asphalt Calculator

How to use the Asphalt Calculator

Work in whatever units you measured in, feet, inches, yards or metres, and the calculator converts as it goes. Three tabs cover the jobs people actually turn up with.

• Area is the everyday one: enter length, width and the compacted depth, pick the mix, and you get tonnage, cubic yards and the square feet a ton covers.
• Coverage runs it backwards. If you already know you can get, say, five tons, it tells you how far that goes at a given depth, useful when the tonnage is fixed and the area is not.
• Cost takes the same measurements and prices them at your supplier’s rate per ton, with an optional delivery or mobilisation fee.

Depth is the one input people get wrong. Enter the compacted thickness, the finished surface after rolling, because that is how asphalt is specified, quoted and sold.

How much asphalt do I need?

Asphalt is bought by weight, not by area, so the amount you need comes from a short chain: the area you are paving, how thick it will be, and how heavy the mix is.

Multiply length by width to get the area, multiply that by the depth to get a volume, then multiply the volume by the density of the mix to get a weight. Divide by 2,000 and you have tons. The calculator does all of this the moment you enter your measurements, but it is worth understanding the chain because it explains why depth and mix change the answer so much, a driveway at three inches needs half as much again as the same driveway at two.

How to calculate asphalt tonnage

If you want to work it through by hand, here is the process the calculator follows.

• Get the area in square feet: length × width.
• Turn the depth into feet: a 2 inch surface is 2 ÷ 12 = 0.167 ft.
• Multiply for volume in cubic feet: area × depth.
• Multiply by the density of the mix in pounds per cubic foot, about 145 for hot mix.
• Divide by 2,000 to convert pounds to US tons.

Then add a small waste allowance. A few per cent covers the material lost to edges, joints and the bit that sticks in the truck bed, and the calculator adds this on top of the raw figure so the number you order is the number you can actually lay.

Asphalt tonnage formula

In one line:

• tons = (length × width × depth) × density ÷ 2,000

Length, width and depth are all in feet, density is in pounds per cubic foot, and the result is US tons before waste. The only figure that is not a measurement is the density, and it depends on the mix:

These are typical compacted densities, and they are enough to order from. The exact figure varies with the mix design and how well it is compacted, which is why the result is an estimate rather than a guarantee.

Asphalt for a driveway

For a normal residential driveway, two inches of compacted surface course is the usual specification; three inches suits a drive that takes trucks or an RV, and a parking lot is four or more. Whatever the surface thickness, it sits on a compacted aggregate base of four to eight inches, that base is a separate material and is not part of the asphalt tonnage.

Measure the drive as a plain rectangle where you can, and break an L-shape or a flare by the garage into rectangles you add together. The calculator’s tonnage is the surface material only; the real quantity on the day can still shift a little with base preparation, compaction, the mix your paver runs, and how much gets trimmed at the edges. On a job of any size it is worth confirming the final figure with the contractor or the asphalt plant before you order.

Asphalt weight and density

Density is what connects the volume you measured to the weight you pay for. Compacted hot mix runs around 145 pounds per cubic foot, roughly 2,320 kg/m³, which is where the rule of thumb that one ton covers about 80 square feet at two inches comes from.

Density is not a fixed number, though. A coarser or lighter mix weighs less, recycled millings are lighter again, and loose asphalt straight off the truck is far less dense than the same material once it has been rolled. Because the calculator works in compacted density, always enter the finished thickness rather than the loose depth, or the tonnage will read high.

Worked example

Take a driveway 60 feet long and 12 feet wide, surfaced 2 inches thick in hot mix.

• Area: 60 × 12 = 720 sq ft.
• Depth in feet: 2 ÷ 12 = 0.167 ft.
• Volume: 720 × 0.167 = 120 cubic feet.
• Weight: 120 × 145 = 17,400 lb, or ÷ 2,000 = 8.70 tons.
• With 5% waste: about 9.14 tons to order.

Running it the other way on the Coverage tab, five tons of hot mix laid two inches thick covers about 414 square feet.

Common mistakes

• Ordering the loose depth. Specifications, quotes and this calculator all mean the compacted thickness after rolling, which is thinner than the loose material you spread.
• Forgetting the base. Asphalt laid straight onto soil cracks and sinks within a season or two. The aggregate base underneath is not optional and is not included in this figure.
• Using one density for every mix. Millings and cold patch are lighter than hot mix, so the same volume is fewer tons, pick the mix before you read the number.
• Skipping a waste allowance. Edges, joints and handling lose a little material, and a driveway that comes up a quarter-ton short means a second delivery.

Frequently asked questions