Compost is sold by volume in litres. To fill a pot or raised bed, multiply Length × Width × Depth (in metres). That gives cubic metres, which you can easily convert into bags.
Start simple — assume 100% compost
For most jobs (filling pots, containers, or a new raised bed), it’s easiest to think in pure MPC first. Later you can tweak or mix with soil if needed — but for buying, plan for compost only.
Quick examples
| Use | Dimensions | Volume | What to buy |
|---|---|---|---|
| Small planter | 40 L | — | One 50 L bag |
| 3 medium tubs (20 L each) | — | 60 L total | One 60 L bag |
| Raised bed 1 m × 2.4 m × 0.3 m | 0.72 m³ | ≈ 720 L | One bulk bag or ~14 × 50 L bags |
| Large border 2 m × 2 m × 0.1 m | 0.4 m³ | ≈ 400 L | 8 × 50 L bags |
Simple rule
Volume (L) = Length (m) × Width (m) × Depth (m) × 1000
Example:
1 m × 2.4 m × 0.3 m = 0.72 m³ → 720 L → about 14 bags of 50 L.
Handy conversions
- 1 m³ = 1000 L
- 1 bulk bag ≈ 700–1000 L (check supplier)
- 1 × 50 L bag covers 0.05 m³
- 1 × 60 L bag covers 0.06 m³
Pro tip
Always round up one bag — compost settles after watering. If you’re filling multiple containers, group them by size and total the volumes before buying.
Summary
Measure first, multiply length × width × depth, and match to bag size:
- 50 L bag = 0.05 m³
- 60 L bag = 0.06 m³
- Bulk bag ≈ 0.7–1.0 m³
For a 1 m × 2.4 m × 0.3 m raised bed, buy roughly one bulk bag (or 14 × 50 L bags). Simple maths — no calculator app needed.
Disclaimer.
Brand names such as Westland, SylvaGrow, RocketGro, Dalefoot, Carbon Gold, and others mentioned on this site are registered trademarks of their respective owners. MultipurposeCompost.co.uk includes these examples for informational and comparative purposes only and does not claim endorsement, affiliation, or suitability for any specific use. Gardeners and buyers should always check current product specifications and manufacturer guidance before purchase or application.
