BuildCalcs Calculate geometric volume first
Volume = area × depth. A 20 m² area at 50 mm uses 20 × 0.05 = 1.00 m³ of geometric volume.
Area/depth reference
| Area | 25 mm | 50 mm | 75 mm | 100 mm |
|---|---|---|---|---|
| 5 m² | 0.12 m³ | 0.25 m³ | 0.38 m³ | 0.50 m³ |
| 10 m² | 0.25 m³ | 0.50 m³ | 0.75 m³ | 1.00 m³ |
| 20 m² | 0.50 m³ | 1.00 m³ | 1.50 m³ | 2.00 m³ |
| 30 m² | 0.75 m³ | 1.50 m³ | 2.25 m³ | 3.00 m³ |
| 40 m² | 1.00 m³ | 2.00 m³ | 3.00 m³ | 4.00 m³ |
| 50 m² | 1.25 m³ | 2.50 m³ | 3.75 m³ | 5.00 m³ |
Why BuildCalcs doesn't hide density
Converting cubic metres to tonnes requires a density. Sand, gravel and other aggregates do not all share one density, and bulk condition and moisture can matter. A supplier-specific figure is preferable when available. Any calculator conversion should therefore identify the density assumption being used.
Worked gravel example
A 7 m × 3 m area is 21 m². At 50 mm, geometric volume is 21 × 0.05 = 1.05 m³. This value can then be converted using the density or coverage information for the actual product.
Worked sand example
A 12 m² area at 30 mm requires 12 × 0.03 = 0.36 m³ geometrically. If the material is being compacted or used as a bedding layer, distinguish the intended finished depth from the loose quantity supplied.
Irregular spaces
Divide irregular areas into rectangles or other simple shapes. Add the component areas before multiplying by depth. This also makes it easier to revisit one measurement if the project changes.
Before buying bulk material
- Confirm depth after preparation/compaction assumptions.
- Use product-specific density or coverage when converting to weight.
- Check bag or bulk-bag quantities with the supplier.
- Keep contingency separate from the base volume.
Enter your actual measurements rather than relying on a generic example.
Open the Gravel Calculator →