Measure bed length, width and fill depth first
Record every relevant dimension in the same unit and separate irregular sections. Small measuring errors multiply across an entire project, so check each figure before adding a waste allowance.
Convert depth correctly
A 20 cm depth is 0.2 m. Multiply length by width by depth in metres to obtain cubic metres, or convert the result to litres for bagged products.
Turn the result into a buying quantity
Calculations produce a net requirement, while shops sell fixed packs. Round up only at the final buying step, compare pack coverage, and keep unopened soil returnable where the retailer permits it.
Practical checklist
- Allow for settlement without overfilling plant crowns.
- Use separate calculations for beds with different depths.