Gravel Calculator

Tonnes and bulk bags of gravel for a driveway, path or border.

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About this calculator

Gravel is ordered by the tonne or the bulk bag, but you measure your driveway in metres — this calculator bridges the two using the material density, and shows bulk-bag and small-bag equivalents.

The formula

Volume = Length × Width × (Depth ÷ 100) Tonnes = Volume × Density (t/m³)

Worked example

A driveway 8m × 3m at 5cm: volume = 1.2 m³ × 1.5 = 1.8 tonnes ≈ 3 bulk bags.

Common mistakes

Spreading gravel too thin to save money — under 4cm it scatters and shows the membrane.
Skipping the weed membrane, then fighting growth through the stones.
Using pea gravel on slopes where it migrates — angular gravel locks together better.

Frequently asked questions

4–5cm for decorative areas and paths, 5cm over a compacted sub-base for driveways (the sub-base itself is separate, typically 10–15cm of MOT Type 1).

1.5 t/m³ suits most 10–20mm gravels; slate chippings ~1.4, limestone ~1.6. Suppliers list exact figures.

Bulk bags (~850kg) are convenient to about 3–4 bags; beyond that a loose tipped load is much cheaper per tonne.

Assumptions & limitations

Uniform depth over a rectangular area; sub-base excluded.

Sources & verification

Aggregate suppliers’ bulk-density data — Loose gravel typically weighs 1.4–1.7 tonnes/m³ depending on stone type and moisture; your supplier’s figure governs

All sources last accessed 24 July 2026.

Formula last verified: 24 July 2026

Maintained by: Steve Davis, Founder & Editor — see our editorial standards

Spotted an error or an out-of-date figure? Report it — corrections are prioritised over all other work (see our corrections policy).

Related guide

How much waste to allow for building materials