How it’s worked out
Volume (m³) = area (m²) × depth (m). Road base is ordered about 25% over the compacted volume, because it shrinks when compacted. Tonnes = volume × the material’s density; landscape suppliers usually sell stone, sand and road base by the tonne, and soil and mulch by the cubic metre.
| Material | Approx. tonnes per m³ | Typical depth |
|---|---|---|
| Mulch | 0.3–0.4 | 50–100 mm |
| Garden soil | about 1.3 | 200–300 mm for raised beds |
| Compost | about 0.6 | 50 mm dug in |
| Gravel and pebbles | 1.5–1.7 | 50 mm for paths |
| Bedding sand | about 1.6 | 20–30 mm under pavers |
| Road base | 1.8–2.0 | 75–100 mm compacted for paths |
Densities vary with moisture and the product, so ask your supplier for theirs. Building a raised bed? See how many sleepers you need. Paving? See road base and sand for pavers.
Questions
How much mulch do I need?
Multiply the garden bed area by the depth. Mulch is usually spread 50–100 mm deep; at 75 mm, each 10 m² of garden needs 0.75 m³, or about 15 × 50 L bags.
How many bags of soil make a cubic metre?
A cubic metre is 1,000 litres: 40 × 25 L bags or 20 × 50 L bags. For more than about 1 m³, buying in bulk from a landscape supplier is usually much cheaper.
How much does a cubic metre of gravel weigh?
Roughly 1.5–1.7 tonnes, depending on the stone. Road base is about 1.8–2.0 tonnes per m³, sand about 1.6, garden soil about 1.3, and mulch much lighter at around 0.3–0.4 tonnes.
Can I carry a cubic metre in a box trailer?
Often not safely. A cubic metre of gravel or road base weighs 1.5–2 tonnes, more than many trailers are rated to carry. Check your trailer’s aggregate trailer mass (ATM) and your car’s towing limit, or get it delivered.
Estimates only. Check the product label and your measurements before you buy. More free tools: see them all.