How to use the Asphalt Calculator
- Enter the area to be paved, measuring each section separately.
- Enter the compacted depth required for the traffic the surface will carry.
- Confirm the mix density with your supplier and enter it.
- Add 5 to 10% for compaction losses, edges and handling.
How the calculation works
Volume is area × compacted depth; tonnage is that volume multiplied by density. Hot mix asphalt typically weighs around 2.3 tonnes per cubic metre compacted, roughly 145 pounds per cubic foot, but the figure varies with aggregate type and mix design, so the supplier's own density is the right input for anything more than a rough estimate.
Depth follows use. Around 40 to 50 mm of surface course is normal for a residential driveway over a sound base, while roads carrying heavy vehicles need considerably more in layers over a properly compacted sub-base. Material laid loose compacts by roughly 20 to 25%, so the depth entered must be the compacted depth — using loose depth understates the tonnage needed.
Tonnes = area (m²) × compacted depth (m) × density (t/m³) × (1 + waste)Source: Typical hot mix asphalt compacted density ≈ 2.3 t/m³ (145 lb/ft³) per Asphalt Institute guidance; confirm mix-specific density with the supplier.
Worked example
A driveway 18 m long and 3.4 m wide, surfaced at 50 mm compacted, mix density 2.32 t/m³.
- Area = 18 × 3.4 = 61.2 m².
- Volume = 61.2 × 0.05 = 3.06 m³.
- Tonnage = 3.06 × 2.32 = 7.10 t.
- Add 7% for edges and handling: 7.60 t.
Order about 7.6 tonnes. Suppliers usually deliver in whole-tonne increments, so 8 tonnes is the practical order.
Frequently asked questions
How thick should a driveway surface be?+
Around 40 to 50 mm of compacted surface course over a sound, well-compacted base is typical for cars. Heavier vehicles need thicker layers and a stronger sub-base.
Why does the density matter so much?+
Asphalt is sold by weight but specified by depth, so density is the bridge between them. A 10% density difference changes the tonnage — and the cost — by the same 10%.
Is the depth I enter loose or compacted?+
Compacted. Loose material reduces by roughly 20 to 25% under the roller, so entering loose depth would leave you short of the finished thickness.
Should I order extra?+
Yes, 5 to 10%. Edges, slight base irregularity and material lost in handling all consume more than the nominal calculation, and asphalt cannot be topped up neatly once it has cooled.
Last reviewed August 31, 2026. We review this page whenever the underlying formula, tax year, published rate or standard changes.