How to Calculate Asphalt — Formulas, Units and Worked Examples
Asphalt tonnage is area times compacted thickness times mix density, divided by 2,000 or 1,000. This guide walks through every step in both unit systems, covers cubic yards and square yards, handles irregular and layered sites, and flags the shortcut constants circulating online that are wrong by a factor of two.
The short version
Imperial: Tons = Area (sq ft) × Thickness (in) ÷ 12 × 145 ÷ 2,000
Metric: Tonnes = Area (m²) × Thickness (m) × 2.3227
Then add 5–15% for waste and compaction before you place the order.
Calculator
Step by step
Step 1 — Measure and calculate the area
Length × width for a rectangle. π × radius² for a circle. Half the base times the height for a triangle. Half the sum of the parallel sides times the height for a trapezoid.
Measure at three points along each dimension and take the largest. Driveways are rarely square, and being 6 inches out over 40 feet is a 1.25% error you will not notice until you run short.
Step 2 — Decide the compacted thickness
This is a structural decision, not an arithmetic one — see the thickness guide. Whatever you choose, make sure it is the compacted figure. Loose thickness behind the paver is about 20% greater.
Step 3 — Put area and thickness into the same units
This is where most errors happen. Area is in square feet or square metres; thickness is in inches or centimetres. Divide inches by 12 to get feet. Divide centimetres by 100 to get metres. Divide millimetres by 1,000.
Step 4 — Calculate the volume
Volume (m³) = Area (m²) × Thickness (m)
Step 5 — Apply the mix density
Weight (kg) = Volume (m³) × Density (kg/m³)
145 lb/ft³ or 2,322.7 kg/m³ for dense-graded hot mix. See the density guide for the other fifteen mix types — the difference between assuming 145 for RAP millings and using the correct 125 is a 16% ordering error.
Step 6 — Convert to tons or tonnes
Metric tonnes = Weight (kg) ÷ 1,000
Step 7 — Add the waste and compaction buffer
The single-constant shortcut, and why most versions of it are wrong
Estimators collapse steps 3 to 6 into one multiplication. The correct constants:
| Working in | Constant | Formula | Check: 1,000 sq ft at 2 in |
|---|---|---|---|
| Square feet, inches | 0.006042 | sq ft × in × 0.006042 | 12.08 tons ✓ |
| Square yards, inches | 0.05438 | sq yd × in × 0.05438 | 111 sq yd × 2 × 0.05438 = 12.07 tons ✓ |
| Square metres, centimetres | 0.023227 | m² × cm × 0.023227 | 92.9 m² × 5.08 cm × 0.023227 = 10.96 t ✓ |
| Square metres, metres | 2.3227 | m² × m × 2.3227 | same as above |
Watch out for 0.0031. You will find this constant on dozens of sites presented as "tons = area × thickness × 0.0031". It is roughly half the square-foot constant and roughly a seventeenth of the square-yard constant, and it does not correspond cleanly to any standard unit combination. Applied to square feet it under-orders by 49%. If you take one thing from this page, take the habit of checking any shortcut against the long-form calculation on a known example before trusting it with a purchase order.
Worked example — imperial
Project: a residential driveway 48 ft long, 14 ft wide, plus a 20 ft × 20 ft parking apron, both at 3 inches of compacted dense-graded hot mix.
- Driveway area: 48 × 14 = 672 sq ft
- Apron area: 20 × 20 = 400 sq ft
- Total area: 672 + 400 = 1,072 sq ft
- Thickness in feet: 3 ÷ 12 = 0.25 ft
- Volume: 1,072 × 0.25 = 268 ft³
- Cubic yards: 268 ÷ 27 = 9.93 cu yd
- Weight: 268 × 145 = 38,860 lb
- Tons: 38,860 ÷ 2,000 = 19.43 tons
- With a 10% buffer: 21.4 tons to order
- At $130/ton: $2,780 in material
- Delivery: 21.4 ÷ 20 = 2 tri-axle loads, the second about 1.4 tons
That last line matters. A 1.4-ton tail load will attract a small-load fee at most plants, and it is worth asking whether bumping the thickness slightly to fill the truck is cheaper than paying it.
Worked example — metric
Project: a car park 32 m by 18 m, built as a 50 mm BBSG wearing course over a 70 mm grave bitume base.
- Area: 32 × 18 = 576 m²
- Wearing course: 576 × 0.05 = 28.8 m³; × 2,370 kg/m³ = 68,256 kg = 68.3 tonnes
- Base course: 576 × 0.07 = 40.3 m³; × 2,385 kg/m³ = 96,116 kg = 96.1 tonnes
- Total: 164.4 tonnes
- With a 10% buffer: 180.9 tonnes to order
- At €95/tonne: €17,186 in material
Note that the two layers use different densities. Running the whole 120 mm at a single 2,322.7 kg/m³ would have given 160.6 tonnes — a 2.4% error, which is inside the buffer but compounds on larger jobs.
Working in cubic yards
Some North American suppliers, particularly for millings, cold mix and base stone, sell by the cubic yard rather than the ton.
| Conversion | Value | Note |
|---|---|---|
| 1 cubic yard | 27 ft³ | Definition |
| 1 cubic yard of dense HMA | 3,915 lb / 1.96 tons | At 145 lb/ft³ |
| 1 cubic yard of RAP millings | 3,375 lb / 1.69 tons | At 125 lb/ft³ |
| 1 cubic yard of crushed stone base | 2,835 lb / 1.42 tons | At 105 lb/ft³ |
| 1 US ton of dense HMA | 0.511 cubic yards | Inverse |
| 1 cubic yard | 0.7646 m³ | Metric |
The calculators on this site output cubic yards and cubic metres alongside tonnage, so you can compare quotes given in different units without converting by hand.
Working in square yards
US state DOTs bid asphalt paving in square yards, and the tonnage is derived from a per-square-yard-per-inch rate.
| Thickness | Tons per sq yd | Sq yd per ton |
|---|---|---|
| 1" | 0.0605 | 16.5 |
| 1.5" | 0.0907 | 11.0 |
| 2" | 0.1210 | 8.3 |
| 2.5" | 0.1512 | 6.6 |
| 3" | 0.1814 | 5.5 |
| 4" | 0.2419 | 4.1 |
| 6" | 0.3629 | 2.8 |
There is a dedicated square yards to tons calculator if you are working from a bid schedule.
Irregular and multi-section sites
Break the site into shapes the arithmetic can handle. Rectangles, triangles, circles, trapezoids. Calculate each, then add.
| Shape | Area formula | Measure |
|---|---|---|
| Rectangle | L × W | Length and width |
| Circle | π × r² | Diameter across the widest point |
| Half circle | π × r² ÷ 2 | Diameter of the full circle |
| Triangle | ½ × base × height | Base and perpendicular height |
| Trapezoid | ½ × (a + b) × h | Both parallel sides and the perpendicular distance |
| Ring / annulus | π × (R² − r²) | Outer and inner diameter |
For genuinely freeform edges, overlay a grid on a scaled site plan and count squares. Anything within 3% is fine — it sits inside the waste buffer.
Multi-layer structures
A layered pavement is not one calculation with a combined thickness. Each layer has its own mix, its own density and often its own price, so calculate them separately:
| Layer | Thickness | Mix | Density | Price/ton | Tonnage on 5,000 sq ft |
|---|---|---|---|---|---|
| Wearing course | 2" | Dense HMA | 145 lb/ft³ | $145 | 60.4 t |
| Binder course | 2.5" | Coarse HMA | 147 lb/ft³ | $120 | 76.6 t |
| Asphalt base | 3" | ATB | 148 lb/ft³ | $105 | 92.5 t |
| Total asphalt | 7.5" | — | — | — | 229.5 t |
| Aggregate base | 8" | Crushed stone | 105 lb/ft³ | $28 | 175.0 t |
Add one area entry per layer in the calculator, each with its own thickness and mix type, and it returns per-layer and combined totals.
Calculating the aggregate base
The stone under the asphalt is usually a larger tonnage than the asphalt itself, and it is routinely left out of estimates.
| Base material | Compacted density | Tons per 1,000 sq ft at 6 in |
|---|---|---|
| Crushed stone (graded aggregate base) | 105 lb/ft³ | 26.3 tons |
| Crusher run / dense-graded aggregate | 110 lb/ft³ | 27.5 tons |
| Recycled concrete aggregate | 100 lb/ft³ | 25.0 tons |
| Wet mix macadam (India) | 2,200 kg/m³ | — |
| Type 1 sub-base (UK) | 2,100 kg/m³ | — |
Note that base stone consolidates more than asphalt during compaction — a 20–25% loss is normal, so use a larger buffer than you would for hot mix.
How much extra to order
| Situation | Buffer | Reason |
|---|---|---|
| Machine-laid rectangle, experienced crew | 5% | Minimal trimming, predictable compaction |
| Standard driveway or lot | 10% | Normal edges and measurement tolerance |
| Curved edges, multiple sections | 15% | More offcuts, more hand work |
| Hand-placed work, small patches | 15% | Hand compaction is less consistent |
| RAP millings | 15–20% | Higher compaction loss, 1.25 factor |
| Cold mix patching | 15–20% | Irregular placement |
| Aggregate base stone | 20–25% | Significant consolidation under rolling |
What your supplier actually needs
Have these ready when you call the plant:
- Tonnage, including your buffer, rounded up to the nearest half ton.
- Mix designation — the plant's own name for it, or the DOT spec number. "Asphalt" is not an order.
- Delivery date and time window. Hot mix cannot wait; the crew has to be ready when it arrives.
- Truck type and site access. Overhead cables, gate widths, turning radius, and whether a live-bottom trailer can reach the paver.
- Discharge method — direct into the paver, into a transfer vehicle, or tipped on the ground for hand work.
- Minimum order and small-load fee. Ask before you calculate, because it may change how you sequence the job.
Where calculations go wrong
- Inches not divided by twelve. A twelvefold error, and the most common one by a wide margin.
- Loose thickness used instead of compacted. Over-orders by about 20%.
- Short tons confused with metric tonnes. A 10% error in either direction.
- 145 lb/ft³ assumed for a mix that is not dense-graded hot mix. Up to 31% out for porous asphalt.
- Excavation dimensions used instead of pavement dimensions. The dig is always wider.
- A layered structure calculated as one combined thickness at one density.
- Base stone forgotten entirely. Often the larger tonnage of the two.
- An unverified online shortcut constant. See the warning above.
Frequently asked questions
How do I calculate asphalt quantity in tons?
Multiply area by compacted thickness to get volume, multiply volume by the mix density, then divide by 2,000 for US short tons or 1,000 for metric tonnes. For a 1,000 sq ft area at 2 inches of dense-graded hot mix: 1,000 × (2÷12) × 145 ÷ 2,000 = 12.08 tons.
What is the formula for asphalt tonnage?
Tons = Area (sq ft) × Thickness (in) ÷ 12 × 145 ÷ 2,000. In metric, Tonnes = Area (m²) × Thickness (m) × 2.3227. Substitute your own density if you are not using dense-graded hot mix.
How do I calculate asphalt in cubic yards?
Calculate the volume in cubic feet, then divide by 27. A 1,000 sq ft area at 3 inches is 250 ft³, which is 9.26 cubic yards. Some suppliers, particularly for millings and cold mix, quote by the cubic yard rather than the ton.
How many tons of asphalt in a cubic yard?
1.96 tons of dense-graded hot mix. One cubic yard is 27 ft³, and at 145 lb/ft³ that is 3,915 lb, or 1.96 short tons. For RAP millings at 125 lb/ft³ it is 1.69 tons per cubic yard.
How do I calculate asphalt for an irregular shape?
Split it into rectangles, triangles and circle segments, calculate each separately, then add the tonnages. The calculators on this site accept unlimited areas with an individual shape and thickness for each, so you can enter the pieces directly instead of adding them by hand.
Should I use loose or compacted thickness?
Compacted, always. Loose mix behind the paver is about 20% bulkier than the finished pavement. If a spec quotes a loose thickness, divide by the compaction factor — roughly 1.20 for dense-graded HMA — before you calculate.
How much extra asphalt should I order?
5% on a simple rectangle with a machine-laid mat and an experienced crew. 10% for a normal driveway or lot. 15% for curved edges, multiple sections or hand work. 15–20% for millings and cold mix.
How do I convert square yards to tons?
Multiply square yards by 9 to get square feet, then apply the standard formula. Or use the DOT shortcut: 1 square yard at 1 inch of dense-graded mix is 0.0605 tons. Multiply by your thickness in inches from there.
How do I calculate the aggregate base as well?
Same geometry, different density. Compacted crushed stone base runs about 100–110 lb/ft³ (1,600–1,760 kg/m³), noticeably lighter than asphalt. A 1,000 sq ft area at 6 inches of base is 500 ft³, which at 105 lb/ft³ is 52,500 lb or 26.3 tons of stone.
Is there a single constant I can memorise?
For dense-graded hot mix in imperial units: tons = sq ft × inches × 0.00604. Several widely circulated shortcuts use 0.0031, which is the square-yard constant and gives an answer nine times too small if applied to square feet. Check any shortcut against the long-form calculation before you trust it.
Sources and further reading
- NAPA — National Asphalt Pavement Association
- AASHTO
- FHWA — Federal Highway Administration
- ASTM International
Related calculators and guides
Density guide
The density values the formula depends on.
Thickness guide
Choosing the depth to calculate against.