Gravel calculator
A gravel or crushed-stone sub-base spreads the load and drains water under paths, foundations and parking areas. The calculator gives its volume and approximate weight, the two numbers suppliers quote in.
Your measurements
Result
- Gravel volume
- 1.50 m³
- Estimated weight
- 2.25 t
The layer settles when compacted — order 10–30% more than the finished thickness, depending on the material.
How the calculation works
- Volume (m³) = length × width × layer thickness.
- Weight (tonnes) = volume × 1.5 t/m³, the average density of loose gravel.
Worked example
A 10 cm layer over 5 × 3 m is 5 × 3 × 0.10 = 1.5 m³ of gravel — about 2.25 tonnes.
What the calculator assumes
- 1.5 t/m³ is an average; ballast and fine crushed stone reach 1.6–1.7 t/m³.
- The layer is spread on excavated, compacted ground; a geotextile underneath stops the gravel mixing with the soil.
When to adjust the result
- Compacted stone settles by 20–30%: for 10 cm finished, order more.
- Driveways use thicker layers (20–30 cm), laid and compacted in two lifts.
Choosing and ordering gravel
Pick the grade by use. Crushed angular stone (for example 0–32 mm) locks together when compacted and makes a stable sub-base; round pea gravel stays loose and is for decorative surfaces or drainage, not under paving. For drainage around foundations and land drains, use washed single-size gravel so water can pass.
Bulk aggregates are sold by the tonne or by the cubic metre — convert with the density on the supplier's data (often 1.5–1.7 t/m³ for loose gravel). Compacted layers need about 10–20% more material than their finished volume, and a tipper load needs a firm, accessible spot close to where you will use it.
Frequently asked questions
How much does a cubic metre of gravel weigh?
Roughly 1.5 tonnes loose, and 1.6–1.7 tonnes for ballast or fine crushed stone.
How deep should a gravel sub-base be?
Around 10–15 cm under footpaths and 20–30 cm under driveways, compacted in layers.
How deep should a gravel driveway be?
Commonly 10–15 cm of compacted crushed stone as a base plus 3–5 cm of surface gravel; soft ground needs more.
Should I use a membrane under gravel?
A geotextile under the gravel stops it sinking into the soil and reduces weeds; it must be permeable so water drains.