Soil & compost
Choose an application depth for your material and project.
- Volume = total area × depth. Extra loose fill is an editable allowance for uneven ground and settlement, not a universal compaction factor.
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Soil & Compost Calculator
Plan soil, compost, topsoil and raised-bed layers with bag or bulk quantities.
Method and practical checks
- Volume = total area × depth. Extra loose fill is an editable allowance for uneven ground and settlement, not a universal compaction factor.
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Every calculation option
Raised-bed layers
Add each material layer separately; existing fill and solid objects reduce the depth you need to fill.
- Each layer deducts its own occupied volume before adding loose-fill allowance. Bags round up separately for each material; surplus compost cannot replace a shortfall of soil.
Topsoil & bulk
Use the supplier’s bulk density and choose bag or bulk delivery quantities.
- Mass = loose volume × entered density. The example density is only a working assumption; moisture and material composition change it.
Worked example
Covering 5 × 4 m at 10 cm deep needs 2 m³ of soil. With a 10% allowance for settling that is 2.2 m³ (2,200 L, about 77.7 ft³), which is exactly 55 bags of 40 L.
| Input | Value |
|---|---|
| Material | Soil |
| Measured sections | Length 5 m, Width 4 m |
| Fill depth | 10 cm |
| Additional loose fill | 10 % |
| Pack size | 40 L |
| Result | Value |
|---|---|
| Net volume | 2 m³ |
| Loose volume | 2.2 m³ |
| Loose volume in cubic feet | 77.692 ft³ |
| Required quantity | 2,200 L |
| Packs to buy | 55 |
| Purchase quantity | 2,200 L |
| Left over | 0 L |
Reading the result
- Bagged soil and compost are sold by loose volume in litres. Bulk deliveries are often sold by weight, so use the supplier’s density for them.
- New raised beds settle; the allowance keeps the surface near the top after the first months.
- Different materials (soil, compost, grit) are rounded separately because surplus compost cannot make up a shortfall of soil.
Sources and further reading
- RHS: mulches and mulching — Organic mulch at least 5 cm and ideally 7.5 cm thick, kept off woody stems.