Asphalt Calculator

What is an asphalt calculator?

An asphalt calculator estimates how much hot-mix asphalt you need to pave a rectangular area and converts that amount into the weight you actually order. You enter the length and width of the area along with the compacted thickness of the layer, and the calculator returns the volume in both cubic feet and cubic yards and the weight in US (short) tons and metric tonnes. Because asphalt is sold by weight at the plant, the tonnage figure is the number that matters when you place an order for a driveway, parking lot, road patch, or path.

How does it work?

A paved layer is a thin rectangular slab, so its volume is simply length times width times thickness. Length and width are typically measured in feet while the paving thickness is measured in inches, so the thickness is divided by 12 to convert it to feet before the three dimensions are multiplied together. That gives a volume in cubic feet, which is divided by 27 to express it in cubic yards, since there are 27 cubic feet in a cubic yard.

Turning volume into weight requires the density of the compacted mix. The calculator multiplies the volume in cubic feet by the density in pounds per cubic foot to get a weight in pounds, then divides by 2000 to convert to US short tons. Compacted hot-mix asphalt has a density of roughly 145 lb/ft³, which is why that value is used as the default; if your mix or aggregate differs you can change it. Metric tonnes are obtained from the US tons by multiplying by 0.90718474.

Formula

For a paved area with length $L$ and width $W$ in feet and thickness $T$ in inches, the volume in cubic feet is:

$V_{ft^3} = L \times W \times \frac{T}{12}$

Converting to cubic yards divides by 27:

$V_{yd^3} = \frac{V_{ft^3}}{27}$

With a compacted density $\rho$ in pounds per cubic foot, the weight in US short tons is the volume times the density divided by 2000 pounds per ton:

$W_{tons} = \frac{V_{ft^3} \times \rho}{2000}$

Metric tonnes follow from the short-ton figure:

$W_{tonnes} = W_{tons} \times 0.90718474$

Worked example

Suppose you are paving a driveway 20 ft long and 10 ft wide with a 4-inch compacted layer of hot-mix asphalt at the default density of 145 lb/ft³.

The volume in cubic feet is:

$V_{ft^3} = 20 \times 10 \times \frac{4}{12} = 66.667 \ \text{ft}^3$

That is $66.667 / 27 = 2.469$ cubic yards. Multiplying the cubic-foot volume by the density and dividing by 2000 gives the weight in US tons:

$W_{tons} = \frac{66.667 \times 145}{2000} = 4.833 \ \text{tons}$

which is about $4.833 \times 0.90718474 = 4.384$ metric tonnes to order from the plant.

Notes

The density value drives the tonnage, so it is worth getting right. A dense-graded surface course sits near 145 lb/ft³, but open-graded, porous, or aggregate-heavy mixes can fall a few pounds either side, and your supplier can give the exact figure for the mix you buy. Because the layer must be measured after compaction rather than as loose material, use the finished thickness the specification calls for.

Suppliers usually sell asphalt in whole-ton increments and may set a minimum order, so round the result up and add a small allowance for waste, uneven subgrade, and the material that clings to the truck and tools. For an irregular footprint, break it into rectangles, size each one separately, and add the tonnages together.

FAQs

Why does the calculator report weight instead of just volume?

Asphalt plants price and load material by weight, so the tonnage is what you actually order and pay for. The volume in cubic feet and cubic yards is still shown because it helps you sanity-check the layer size and compare against ready-mix or aggregate quantities.

What density should I use for hot-mix asphalt?

Compacted hot-mix asphalt is close to 145 lb/ft³, which is the default here. If your supplier quotes a different unit weight for the specific mix, enter that value instead so the tonnage matches what will be delivered.

What is the difference between US tons and metric tonnes?

A US (short) ton is 2000 pounds, while a metric tonne is 1000 kilograms, or about 2204.6 pounds. A metric tonne is therefore roughly 10% heavier than a US ton, which is why the calculator shows both and converts between them.