Formula used
Rectangular area equals length multiplied by width. Circular area uses π times radius squared. Each section uses its selected geometry.
Volume equals area multiplied by net depth. Net depth subtracts existing material from target depth. Allowances increase the final purchase volume.
Rectangle: Area = Length × Width Circle: Area = π × (Diameter ÷ 2)² Triangle: Area = ½ × Base × Height Trapezoid: Area = ((Base 1 + Base 2) ÷ 2) × Height Tree ring: Area = π ÷ 4 × (Outer Diameter² − Inner Diameter²) Base Volume = Area × Net Depth × Quantity Adjusted Volume = Base Volume × (1 + Total Allowance ÷ 100) Bags = Adjusted Volume ÷ Bag Volume Weight = Adjusted Volume × Bulk Density
How to use this calculator
Choose the units and wood-chip material. Add every bed, path, ring, or play area. Enter each target and existing depth.
Add waste, settling, compaction, and ground allowances. Enter bag sizes or bulk delivery capacity. Add prices for a full estimate.
Submit the form to view results. Compare bag and bulk purchasing totals. Export the final calculation for later use.
Recommended coverage depths
| Use | Typical depth | Planning note |
|---|---|---|
| Light decorative layer | 1 inch | Best for a thin surface refresh. |
| Existing mulch refresh | 2 inches | Measure the remaining depth first. |
| General landscaping | 3 inches | Common for beds and borders. |
| Weed suppression | 4 inches | Keep chips away from plant stems. |
| Pathways | 5 inches | Include settling and compaction allowances. |
| Playground areas | 6 inches or specified | Follow local safety requirements and product guidance. |
Example data
| Section | Shape | Dimensions | Depth | Quantity |
|---|---|---|---|---|
| Front bed | Rectangle | 12 ft × 8 ft | 3 in | 1 |
| Tree rings | Tree ring | 6 ft outer, 1 ft inner | 3 in | 3 |
| Garden path | Pathway | 30 ft × 3 ft | 4 in | 1 |
Frequently asked questions
How deep should wood chips be?
Three inches suits many garden beds. Paths often need four or five inches. Site conditions can change the ideal depth.
Should existing chips be subtracted?
Yes, measure the usable remaining layer. Enter that depth for each section. The calculator uses only the required top-up.
Why include settling and compaction?
Loose chips compress after installation and weathering. Extra material helps preserve the planned finished depth. Paths usually need larger allowances.
How are tree rings calculated?
The tool subtracts the inner circle. This leaves only the chip-covered ring. Multiply quantity for several identical trees.
Can I calculate irregular areas?
Measure or estimate the total surface area. Choose the custom total area option. Enter the figure using your selected area unit.
How accurate are weight estimates?
Weight changes with species, chip size, and moisture. Preset densities provide planning estimates only. Supplier density gives better results.
Should I buy bags or bulk chips?
Bags suit small projects and easier handling. Bulk deliveries usually suit larger coverage needs. Compare access, cost, and storage space.
What is a reasonable waste allowance?
Five to ten percent is common. Irregular edges can require more material. Adjust the value for site complexity.
Can this estimate playground fibre?
Yes, choose playground wood fibre. Enter the required safety depth carefully. Follow local rules and manufacturer specifications.
Why does the calculator round bags upward?
Suppliers sell complete bags, not fractions. Rounding prevents an immediate material shortage. Reserve bags are added afterwards.
Does the total include delivery and tax?
Yes, when those values are entered. Discounts reduce the material cost first. Tax applies to the adjusted project subtotal.