Asphalt Calculator
Find how many tons of hot mix asphalt (blacktop, or tarmac in the UK) you need for a driveway, path, or parking area. Enter the size and the compacted thickness, and see the weight in US tons or tonnes, the volume, and the cost.
Add more areas, or subtract areas that need no asphalt, such as a planter.
- Choose US or Metric. You can still change the unit of any single field.
- Pick the Shape of the area and enter its dimensions. Use Add section for more areas, and set a section to Subtract for parts that need no asphalt.
- Enter the Compacted thickness, as in your plans or quote, not the loose thickness right after spreading.
- Check the Density and the Waste allowance. They start at 146.7 lb/ft³ (2.349 t/m³) and 5%.
- Optionally, enter a price per US ton, tonne, cubic yard, cubic foot, or cubic meter to estimate the cost.
Dimension and thickness fields accept whole numbers, decimals, fractions,
and mixed numbers, such as 20, 12.5, 3/4, or
2 1/2.
How to calculate asphalt tonnage
Asphalt is sold by weight. The calculator finds the volume of the compacted layer, adds the waste allowance, and multiplies by the density:
Volume = area × compacted thickness × (1 + waste % ÷ 100)
Weight = volume × density, US tons = pounds ÷ 2,000
With several sections, the calculator adds the sections set to Add and subtracts those set to Subtract. The area of each shape is calculated as follows:
| Shape | Area |
|---|---|
| Rectangle | length × width |
| Circle | π × diameter² ÷ 4 (or π × radius²) |
| Triangle (base and height) | base × height ÷ 2 |
| Triangle (three sides) | Heron's formula: √(s(s − a)(s − b)(s − c)), where s = (a + b + c) ÷ 2 |
| Trapezoid | (parallel side A + parallel side B) ÷ 2 × height |
| Ring | π × (outer diameter² − inner diameter²) ÷ 4 |
| Rectangular border | outer length × outer width − (outer length − 2 × border width) × (outer width − 2 × border width) |
| Known area | the area you enter |
Asphalt density
The Asphalt Institute's Asphalt magazine article "Five handy rules of thumb for successful asphalt pavement construction" gives a typical spread rate of 110 lb per square yard per inch of thickness for asphalt mixtures. That is 146.7 lb/ft³, or 1.98 US tons per cubic yard (2.349 t/m³), and the calculator uses it as the default density.
The rate varies by mix. The same article notes that the Illinois DOT uses 112 lb per square yard per inch, and that the Tennessee DOT uses 106 lb for most of its dense-graded mixes. Those are about 149 and 141 lb/ft³. If your supplier gives a density for its mix, enter it in the Density field. A spread rate in lb per square yard per inch, divided by 0.75, gives lb/ft³. In the UK, Heidelberg Materials' asphalt calculator says one tonne covers 14 to 18 m² at 25 mm. At the default density, one tonne covers 17.03 m².
Compacted thickness
Hot mix asphalt is spread loose and rolled down to its final thickness. The same Asphalt magazine article recommends setting the paver screed at 1.25 times the final compacted thickness. Rolling does not change the weight, so the tonnage comes from the compacted thickness and the compacted density. Enter the thickness after rolling.
Extra asphalt for waste
Holcim UK's Asphalt Calculator suggests allowing a 5% margin, so the waste allowance starts at 5%. It covers hand work at the edges and an uneven base. You can change it from 0% to 100%. Plants and contractors set their own minimum orders and load sizes, so the calculator does not round the tons up.
Examples
A driveway
A driveway 20 ft × 40 ft with 2 in of compacted asphalt is 800 × 2 ÷ 12 = 133.33 ft³. The area is 88.89 yd², and at 110 lb per square yard per inch, that is 88.89 × 2 × 110 = 19,556 lb, or 9.78 US tons. With a 5% waste allowance, order 10.27 US tons.
Metric dimensions
An area 10 m × 5 m with a 40 mm layer is 2 m³. At 2.349 t/m³, that is 4.70 tonnes before the waste allowance.
FAQ
At the default density, one US ton covers about 81.8 ft² at 2 in thick, or 54.5 ft² at 3 in. One tonne covers about 8.5 m² at 50 mm.
About 1.98 US tons, or 3,960 lb, at the default density of 146.7 lb/ft³. A cubic meter weighs about 2.35 tonnes.
A US ton, or short ton, is 2,000 lb. A tonne, or metric ton, is 1,000 kg, about 2,205 lb. The calculator shows both so you can match your supplier.
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