Volume first, weight second
Asphalt is usually ordered by weight, but the calculation starts with compacted volume. Multiply paved area by the specified finished layer depth, then multiply by compacted mix density. Keeping those steps visible makes it easier to check whether a supplier-specific density changes the result.
Worked example
A 10 m × 4 m area at 5 cm compacted depth has a 2.0 m³ base volume. At 2.4 t/m³ that is 4.8 tonnes before allowance. Adding 5% gives about 5.04 tonnes.
Why depth sensitivity matters
A change of only 1 cm across a 40 m² driveway changes the compacted asphalt volume by 0.4 m³. At 2.4 t/m³, that is almost a tonne before allowance. The planning panel therefore compares a shallower and deeper scenario instead of presenting the chosen depth as if it were perfectly certain.
Compacted depth is not loose depth
Hot mix is placed loose and compressed by rolling. The finished compacted layer is the quantity basis you should use when the project specification gives a target thickness. Entering the loose screed depth as though it were the final thickness can materially distort the estimate.
Supplier density and order increments
| Input | Why it matters | Best source |
|---|---|---|
| Compacted depth | Controls volume directly | Project specification or contractor. |
| Mix density | Converts volume to weight | Asphalt plant / mix data. |
| Order increment | Controls purchase rounding | Supplier quote. |
| Extra allowance | Covers field variation | Project-specific judgement. |
Keep the aggregate base separate
The asphalt result covers the asphalt layer only. A driveway or parking area may have a much thicker aggregate base underneath, but that layer uses a different material and density. Estimate it separately with the Gravel Calculator rather than treating the entire pavement depth as asphalt.
Before ordering asphalt
- Confirm finished compacted layer depth.
- Use the supplier’s density when available.
- Measure width changes as separate sections.
- Ask about minimum loads and order increments.
- Plan delivery, access and compaction before the truck arrives.