Tree Mulch Ring Calculator
Calculate how much mulch you need for a tree ring.
Enter tree trunk diameter, ring width, and depth to get volume in cubic feet or cubic meters.
Mulch Needed
Tree mulch ring volume is calculated as the area of the ring (donut shape) times the depth.
Ring Area = π × (Outer Radius² - Inner Radius²)
Volume = Ring Area × Depth
Where:
- Inner Radius = trunk radius + 3–6 inches (keep mulch away from trunk)
- Outer Radius = inner radius + ring width
Mulch ring best practices:
- Width: 3–6 feet from the trunk (wider is better)
- Depth: 2–4 inches (never more than 4 inches)
- Gap: Keep mulch 3–6 inches away from the trunk to prevent rot
- Shape: Flat and even — never piled against the trunk (“volcano mulching” kills trees)
Mulch sold in:
- Bags: 2 cubic feet per bag (typical)
- Bulk: By the cubic yard (1 cu yd = 27 cu ft)
Coverage per cubic yard at different depths:
| Depth | Coverage |
|---|---|
| 2 inches | 162 sq ft |
| 3 inches | 108 sq ft |
| 4 inches | 81 sq ft |