Gravel and aggregates are ordered by weight but spread by volume, which is why estimating them confuses people. This calculator bridges the two, giving you the volume, the tonnage to order, and a cost estimate.
From area to tonnes
First we find the volume — the area to be covered multiplied by the depth of gravel. Then we convert that volume to weight using the material's density, because suppliers sell and price aggregates by the tonne or ton, not by the cubic metre.
Depth matters more than you'd think
The right depth depends on use. Too shallow and the ground shows through or the surface ruts under traffic; too deep wastes material and feels loose underfoot. Decorative areas want a couple of inches, while driveways need more over a solid sub-base.
Frequently asked questions
Multiply the area by the depth to get the volume, then multiply by the gravel's density (about 1.5 t/m³) to get the weight to order. This calculator gives you both the volume and the tonnage.
For decorative areas, 4–5 cm (about 2 inches) is enough. Driveways and paths that carry traffic need 8–10 cm (3–4 inches) or more, ideally over a compacted sub-base.
Roughly 1.5 tonnes per cubic metre for typical gravel, though it ranges from about 1.4 to 1.7 depending on the stone type, size and moisture content.