Formula Used
Rectangle: Area = Length × Width
Circle: Area = π × Radius²
Triangle: Area = Base × Height ÷ 2
Tree ring: Area = π × (Outer radius² − Inner radius²)
Base volume: Area × Net mulch depth
Final volume: Base volume × Waste factor × Compaction factor
Cubic yards: Square feet × Depth in inches ÷ 324
How to Use This Calculator
- Select the project application and area shape.
- Enter dimensions using one consistent dimension unit.
- Set desired depth and existing mulch depth.
- Add waste and compaction allowances when needed.
- Choose material, bag size, and pricing details.
- Calculate, compare costs, then export your results.
Recommended Mulch Depths
| Application | Typical depth | Practical note |
|---|---|---|
| New garden bed | 3 inches | Blocks weeds and conserves moisture. |
| Existing garden bed | 2 inches | Top up after checking remaining depth. |
| Tree ring | 3 inches | Keep mulch away from the trunk. |
| Pathway | 4 inches | Use fabric underneath when appropriate. |
| Playground | 9 inches | Follow local impact-safety requirements. |
| Compost top-dressing | 1 inch | Avoid burying plant crowns. |
Example Calculation
| Input | Example value |
|---|---|
| Bed size | 20 ft × 10 ft |
| Desired depth | 3 inches |
| Waste allowance | 10% |
| Compaction allowance | 5% |
| Bag size | 2 ft³ |
| Approximate result | 28.88 bags before rounding |
Bag Coverage Reference
| Bag size | At 2 inches | At 3 inches | At 4 inches |
|---|---|---|---|
| 1 ft³ | 6 ft² | 4 ft² | 3 ft² |
| 1.5 ft³ | 9 ft² | 6 ft² | 4.5 ft² |
| 2 ft³ | 12 ft² | 8 ft² | 6 ft² |
| 3 ft³ | 18 ft² | 12 ft² | 9 ft² |
Frequently Asked Questions
How deep should mulch be?
Most beds need two to three inches. Paths often need more depth.
Should existing mulch be removed first?
Usually, measure it before adding more. Remove compacted or mouldy material.
Why add a waste allowance?
Waste covers uneven ground, spillage, and measurement differences.
What does compaction allowance mean?
Some materials settle after spreading. Extra volume helps preserve final depth.
Is bagged mulch or bulk mulch cheaper?
Bulk is often cheaper for large areas. Delivery changes the comparison.
How many square feet does one bag cover?
Coverage depends on bag volume and depth. Use the reference table.
Can this calculator handle tree rings?
Yes. Enter outer and inner diameters for the ring area.
Can I calculate several identical beds?
Yes. Enter the number of matching areas before calculating.
How is existing depth deducted?
The calculator subtracts existing depth from desired final depth.
Does the calculator include tax and labour?
Yes. Add delivery, labour, and tax for complete estimates.
Should mulch touch a tree trunk?
No. Leave a clear gap around trunks and plant stems.