How this calculator works
Volume = area x depth. Purchase volume = volume x (1 + waste / 100). Bags = round up(liters / bag volume).
Worked example
A 5 m x 3 m bed at 5 cm deep is 0.75 m3. With 10% waste that is 0.825 m3 (825 L), or 14 bags at 60 L each.
Assumptions to check
- The bed or border is treated as a flat rectangle.
- Depth should match the product and purpose - ground cover mulch and play-safety bark often need different minimum depths.
- Bag volume (liters) is printed on the bag; bulk (loose or bark-chippings bulk bags/tonnes) suppliers may quote by cubic yard or tonne instead.