Work out how many tonnes of asphalt you need for a driveway, car park or path — enter the area and thickness and get the weight and estimated cost.
| Item | Value |
|---|
Crushed rock and gravel are essential materials in Australian construction and landscaping. They are sold by weight (tonne) or volume (m³) depending on the supplier.
| Application | Material | Depth |
|---|---|---|
| Residential driveway | Dense grade | 25–40 mm |
| Car park | Hot mix | 40–50 mm |
| Footpath / path | Fine asphalt | 25–30 mm |
| Road base course | Hot mix | 50–75 mm |
| Overlay / resurface | Dense grade | 25–30 mm |
A driveway 10 metres long and 4 metres wide paved at 40 mm has an area of 40 m². Volume is 40 × 0.04 = 1.6 m³. Hot-mix asphalt is about 2400 kg/m³, so that’s 1.6 × 2400 = 3840 kg, or 3.84 tonnes. Adding 10% for compaction and wastage gives about 4.2 tonnes to order.
The durability of an asphalt surface depends as much on what’s underneath as on the asphalt itself. A properly compacted road-base foundation — usually 100 mm or more of crushed rock — is essential; asphalt laid over soft or uneven ground will crack, sink and pothole no matter how good the mix is. The base should be graded to drain water away, because trapped water is the main enemy of asphalt longevity. On a solid base, a residential driveway of 25–40 mm of dense-grade hot mix will last for many years.
Timing and compaction matter too. Hot-mix asphalt has to be laid and rolled while it’s still hot, which is why it’s delivered in insulated trucks and worked quickly — this is the main reason larger jobs are best handled by contractors with the right equipment. For small repairs and patching, cold-mix asphalt is available in bags and can be worked by hand, though it’s less durable than hot mix. When ordering, always round up: asphalt is sold by the tonne, a part-load still incurs delivery, and having slightly too much is far better than stopping a pour halfway because you ran out.
The right asphalt thickness depends entirely on what will drive or park on the surface. A residential driveway carrying cars and the occasional delivery van is fine at 25–40 mm of dense-grade hot mix over a good base. Car parks, shared driveways and anything taking heavier or more frequent vehicle traffic need 40–50 mm or more, and commercial or industrial areas thicker still. Going too thin to save on material is a false economy — an underspecified surface cracks, ruts and potholes far sooner, and repairs cost more than the material saved. Because the thickness you enter feeds directly into the tonnage, it’s worth deciding the correct depth for your traffic before ordering, rather than working backwards from a budget.
| Gravel Type | Bulk Density | Common Use |
|---|---|---|
| Pea gravel / river pebbles | ~1.5-1.6 t/m³ | Garden beds, decorative |
| Crushed rock (20mm) | ~1.8-1.9 t/m³ | Driveways, drainage |
| Blue metal (20mm) | ~1.9-2.0 t/m³ | Concrete aggregate, driveways |
| Decomposed granite | ~1.6-1.8 t/m³ | Paths, driveways |
| Road base (compacted) | ~2.0-2.2 t/m³ | Sub-base for driveways |
| Application | Recommended Depth |
|---|---|
| Decorative garden bed | 40-50 mm |
| Landscaping path | 50-75 mm |
| Residential driveway | 75-100 mm over compacted base |
| Drainage layer | 100-150 mm |
How do I calculate how much asphalt I need?
Multiply the area (length × width) by the thickness in metres to get the volume in cubic metres, then multiply by the asphalt density — about 2.4 tonnes per cubic metre for hot mix. This asphalt calculator does it for you and adds a wastage allowance. Asphalt is ordered by the tonne.
How many tonnes of asphalt do I need per square metre?
At a typical 40 mm thickness, one square metre of hot-mix asphalt weighs about 96 kg, so roughly 10.4 m² per tonne. Thicker layers use more per square metre — the calculator shows your exact figure once you enter the thickness.
How thick should an asphalt driveway be?
A residential asphalt driveway is usually laid 25–40 mm thick over a compacted base. Car parks and areas taking heavier vehicles need 40–50 mm or more. Enter your chosen thickness above to get the tonnage.
Is asphalt sold by the tonne or cubic metre?
Asphalt is normally sold and delivered by the tonne. This calculator gives you both the volume in cubic metres and the weight in tonnes so you can order confidently, with a wastage margin included.
How thick should an asphalt driveway be?
A residential asphalt driveway is usually 25–40 mm of dense-grade hot mix over a compacted road base. Areas carrying heavier vehicles need 40–50 mm or more. The thickness directly affects the tonnage required.