Raised-bed compost calculator.
Measure the space you actually need to fill. Get the volume, material split and bag count without wrestling with unit conversions.
- Metric or imperial
- Multiple beds
- No signup
Total material to order
950 litres0.95 cubic metresMaterial split
What to order
570 litres · 0.57 m³
285 litres · 0.29 m³
95 litres · 0.1 m³
Turn the finished space into a dated crop plan, then swap crops or print the year as an A4 chart.
Bag comparison
If buying small bags
- 40 L bags
- 24
- 50 L bags
- 20
- 60 L bags
- 16
Or roughly 2 × 700 L bulk bags. Supplier bulk-bag volumes vary, so check the listing.
Not suitable for structural loading decisions.
Base volume before settlement: 864 litres. The result includes your 10% allowance and rounds bag quantities up.
Measure carefully
Use the internal dimensions.
Measure inside the boards, then enter only the depth that still needs filling. If a bed already contains 20 cm and you want 30 cm, the calculator orders the missing 10 cm—not the full frame.
Understand the estimate
Volume is firm. Weight is not.
The volume uses length × width × missing depth. The handling-weight range is deliberately broad because moisture, texture and compaction vary by product.
Raised-bed soil quantity
Check the volume before choosing the bags.
The dependable part is the geometry. The right material mix depends on whether you are filling a new deep bed or topping up an established one.
| Internal bed size | Fill depth | Basic volume | 50 litre bags |
|---|---|---|---|
| 1.2 × 1.2 m | 15 cm | 216 litres | 5 bags |
| 1.2 × 2.4 m | 15 cm | 432 litres | 9 bags |
| 1.2 × 2.4 m | 30 cm | 864 litres | 18 bags |
| 0.9 × 1.8 m | 20 cm | 324 litres | 7 bags |
Bag counts round up and exclude settlement. If the bed already contains soil, calculate only the missing depth. Use the calculator above for exact dimensions, multiple beds and your chosen allowance.
Questions before ordering
Soil, litres and bags
How do I calculate the soil quantity for a raised bed?
Multiply the internal length by the internal width by the depth that still needs filling. Metric dimensions give cubic metres; multiply cubic metres by 1,000 for litres. Add a settlement allowance only after calculating the basic volume.
How much soil is needed for a 2.4 m by 1.2 m raised bed?
At 15 cm fill depth the basic volume is 432 litres. At 30 cm it is 864 litres. These figures exclude settlement and assume the full depth is empty; enter the current fill depth in the calculator if soil is already present.
Should a raised bed be filled with compost only?
Not automatically. A permanent deep bed commonly needs a suitable soil-based mix, while mature compost is often used as part of a new-bed mix or as a surface top-up. Match materials to the crop, existing soil and supplier guidance.
How many compost bags do I need for a raised bed?
Divide the required litres, including any chosen settlement allowance, by the bag size and round up to a whole bag. The calculator compares 40, 50 and 60 litre bags and can estimate cost from your price per bag.