Gravel Calculator
Estimate gravel for a path, driveway or border. Gravel is usually sold by weight, so this gives you tonnes and tons as well as volume.
How we calculate
We calculate volume from your area and depth, then multiply by a typical density for the material you chose to get a weight, because gravel is sold by the tonne. Weights are rounded up to the nearest 0.05 tonne.
Tip: Loose gravel compacts as it beds in, so ordering about 10% over the calculated figure is normal.
Assumptions & things to watch
- Loose gravel compacts around 10–15%; order slightly over rather than under.
- Driveways need a compacted sub-base beneath the decorative layer — this calculator covers one layer at a time.
- Densities are typical dry values and vary by quarry and stone size.
Estimates only — always double-check quantities with your supplier before ordering.
Quick tips: Gravel
How deep should gravel be?
About 2 in (5 cm) for a footpath or decorative border, and 4 in (10 cm) or more of decorative stone over a compacted sub-base for a driveway.
How much area does a tonne of gravel cover?
A tonne of typical 20 mm gravel covers roughly 12–14 m² (130–150 sq ft) at 2 in (5 cm) deep, or half that at 4 in (10 cm).
How much does gravel cost?
Bulk gravel is usually $40–$80 per tonne delivered depending on stone type and distance. Bulk bags cost more per tonne but suit small jobs.
Do I need a membrane under gravel?
A geotextile membrane stops the stone sinking into the soil and slows weed growth. It's worth it on any path or driveway you expect to last.
What size gravel should I use?
10–20 mm stone is comfortable underfoot for paths. Driveways do better with 20 mm angular stone, which locks together instead of rutting under tyres.