Gravel Calculator
Enter your area and depth in millimetres to see how many cubic metres and tonnes of road base, crushed rock and decorative pebbles you need, and what it should cost in AUD.
Formulas shown on this page · Last reviewed October 2026
How the gravel calculator works
volume (m³) = length (m) × width (m) × depth (mm) ÷ 1,000
tonnes = volume × (1 + extra) × density (t/m³)
Gravel is sold by weight, so the calculator multiplies volume by an approximate loose density. Crushed rock and base materials are roughly 1.6 t/m³ and rounded decorative stone about 1.5 t/m³, but moisture and grading change this – ask your supplier for their figure and edit the density above. The default extra of 10% allows for compaction and uneven ground.
Typical gravel depths
| Use | Depth |
|---|---|
| Decorative gravel on a garden path | 40–50 mm |
| Gravel driveway surface | 50–75 mm |
| Road base, compacted in layers (often 100 mm or more under pavers and driveways) | 100–150 mm |
| Drainage trench or French drain | Fill to trench depth |
Buying gravel in Australia
Landscape supplies yards sell gravel by the cubic metre or by the tonne, loaded onto a trailer or delivered by tipper truck. Popular choices include road base, crushed rock and decorative pebbles. In wet northern regions and on reactive clay soils, a free-draining crushed rock base helps keep paths and driveways from softening and shifting.
Landscape yards usually quote per tonne, with a minimum load and a delivery fee, so your tonnage matters more than a bag count.
At the default price of $65 per tonne for road base (crushed rock, compacting), one cubic metre (about 1.6 tonnes) costs roughly $104.00. These are typical prices – check your local supplier, as delivery charges and minimum loads vary by region.
Frequently asked questions
How much gravel do I need for a 5 × 3 m area at 75 mm deep?
The base volume is 1.125 m³. Adding 10% gives 1.24 m³, which is about 1.98 tonnes at 1.6 t/m³.
How many tonnes of gravel are in a cubic metre?
Roughly 1.5–1.6 tonnes for most crushed and decorative gravel, so 1.6 t/m³ is used as the default here. The exact figure depends on the material and moisture.
Is gravel sold by the cubic metre or the tonne?
Landscape yards use both. The calculator shows 1.24 m³ and 1.98 tonnes for the example above, so you can compare quotes either way.
How much extra gravel should I add?
Around 10% is a sensible allowance for compaction, uneven ground and spillage. Add more under pavers or driveways where the base is compacted hard.