Gravel & Aggregate Calculator
Work out how much gravel, crushed rock, sand, road base, topsoil or mulch an area needs, in cubic metres or yards and in tonnes.
How many cubic metres and tonnes to order for the area.
How the gravel & aggregate calculator works
Bulk materials are sold by volume or by weight, so you need both: volume is area × depth, and weight is volume × bulk density. Gravel and crushed rock weigh about 1.5–1.7 tonnes per cubic metre loose; sand 1.5; topsoil 1.2; mulch only 0.4. A 50 mm layer of gravel over 15 m² is 0.75 m³ — about 1.2 tonnes.
Allow extra for compaction and uneven ground: the with-extra row adds 10%.
Formula: volume = area × depth · tonnes = volume × bulk density
Worked examples
| Inputs | Volume needed | Note |
|---|---|---|
| 5 × 3 m at 50 mm, gravel | 0.75 | 0.75 m³ — 1.2 t |
| 5 × 3 m at 100 mm, mulch | 1.5 | 1.5 m³ but only 0.6 t |
| 16 × 10 ft at 2 in, road base | 0.988 | 0.99 yd³ |
FAQFrequently asked questions
How many tonnes is a cubic metre of gravel?
About 1.5–1.7 loose, depending on the stone and moisture. Suppliers quote their own figure — use it if you have it.
How deep should gravel be?
50 mm for a decorative top layer over a base; 75–100 mm for paths; 100–150 mm compacted road base under a driveway.
Does gravel compact?
Yes — crushed rock and road base lose 10–20% of loose volume when compacted. The with-extra row covers ordinary settlement.
How much does a trailer hold?
A standard 6 × 4 ft box trailer takes roughly 0.5 m³ level — about 0.8 tonnes of gravel, near its legal limit.
Where these figures come from
- The Engineering ToolBox — material densities, coverage and unit data — bulk densities, concrete at 2,400 kg/m³, board and sheet sizes
- Cement Concrete & Aggregates Australia — concrete basics and yields — bag yields, density 2,400 kg/m³
- Australian Building Codes Board — the National Construction Code
Last checked: September 2026. Coverage rates and material sizes are typical manufacturer figures — check the product you buy.