Compost Calculator
Enter the dimensions of your bed, border, pot or planter to get an instant estimate of how much compost you need in cubic metres, litres, and standard bags.
Compost Volume Calculator
Enter your area dimensions to see how much compost is needed
Flower beds: 5-7.5cm • Raised beds: 15-30cm • Pots: 20-30cm
Used to estimate how many bags to order
Estimated Compost Needed
Calculated from your area and depth
Compost Depth Reference Chart
Recommended compost depths for common garden projects. Use this to choose the right depth before calculating your volume above.
| Project Type | Recommended Depth | Litres per m² | Notes |
|---|---|---|---|
| Flower Beds & Borders | 5-7.5cm | 50-75 | Work into existing topsoil |
| Vegetable Beds | 10-15cm | 100-150 | Improves soil structure and nutrients |
| Raised Beds | 20-30cm | 200-300 | Often mixed with topsoil, 50/50 blend |
| Container Pots & Planters | 20-30cm | 200-300 | Fill most of the container depth |
| New Lawn Top-Dressing | 1-2cm | 10-20 | Thin layer raked into surface |
Compost Calculator FAQ
Everything you need to know about working out how much compost your garden project needs.
Multiply the bed’s length, width and depth in metres to get the volume in cubic metres, then multiply by 1000 to convert to litres. A raised bed 2m long, 1m wide and 0.3m deep needs 0.6 cubic metres, or 600 litres, of compost.
One cubic metre is equal to 1000 litres, so you need approximately 20 standard 50 litre bags of compost to fill one cubic metre of space.
For flower beds and borders, a depth of 5 to 7.5cm of compost worked into the topsoil is typical. Vegetable beds and raised planters generally benefit from a deeper layer of 15 to 30cm.
For areas larger than around 2 to 3 cubic metres, loose bulk compost delivered by the tonne bag or trailer load is usually more cost-effective per litre than buying multiple small bags.