How to use the mulch calculator
- Add each bed. Choose rectangle, circle, tree ring or a known area in square feet. Curvy beds can be approximated by a rectangle or circle of similar size, or split into several pieces.
- Use tree rings for trees. Enter the outside diameter of the ring and the trunk diameter — the calculator leaves the area around the trunk bare, which is better for the tree anyway.
- Choose a depth. 2–3 in for most beds, 3–4 in around trees and shrubs, 9 in or more under play equipment.
- Pick a bag size. 2 cu ft is the most common bag in US garden centers; the table shows every size at once.
How to calculate how many bags of mulch you need
Circle area = π × (diameter ÷ 2)²
Tree ring area = π × [(ring diameter ÷ 2)² − (trunk diameter ÷ 2)²]
Cubic feet = total area × depth (in) ÷ 12
Bags = cubic feet ÷ bag size → round up · Cubic yards = cubic feet ÷ 27
A handy rule: one cubic yard of mulch covers 324 sq ft at 1 in deep. Divide 324 by your depth to see how far a yard goes — 162 sq ft at 2 in, 108 sq ft at 3 in, 81 sq ft at 4 in.
Worked examples
How much mulch do I need for 200 square feet?
At 3 in deep, 200 sq ft × 3 ÷ 12 = 50 cu ft = 1.85 cubic yards. That’s 25 bags of 2 cu ft, 17 bags of 3 cu ft or 34 bags of 1.5 cu ft.
Mulch for a circle
A round bed 10 ft across has an area of π × 5² = 78.5 sq ft. At 3 in deep it needs 19.6 cu ft, or 10 bags of 2 cu ft.
A whole front yard
Two 20 × 4 ft foundation beds (160 sq ft) plus three tree rings 6 ft across around 1 ft trunks (82.5 sq ft) total 242 sq ft. At 3 in that’s 60.6 cu ft — 31 bags of 2 cu ft or 2.25 cubic yards in bulk. This is right around the point where bulk delivery starts to beat bags on price.
Depth guide and buying tips
- Don’t over-mulch. More than about 4 in can starve roots of oxygen and hold too much water. For refreshing an existing bed, 1 in on top of the old layer is usually enough.
- No “mulch volcanoes”. Keep mulch a few inches away from tree trunks and shrub stems to prevent rot and pests.
- Playgrounds need depth. The US Consumer Product Safety Commission’s Public Playground Safety Handbook calls for a compressed depth of at least 9 in of wood mulch or wood chips, with the protected fall height depending on the material. Because loose fill compresses by about 25%, it suggests installing about 12 in. Material also gets kicked out over time, so top it up regularly.
- Bulk vs bags. One cubic yard is 13.5 bags of 2 cu ft. Above 2–3 yards, bulk is usually cheaper even with a delivery fee — but you’ll need a tarp, a wheelbarrow and a free afternoon.
- Lay it after weeding and edging, and water it lightly after spreading to help it settle.
Prefer stone? Use the gravel calculator for river rock and pea gravel. Fixing a soggy bed first? Start with the French drain calculator.
Mulch coverage chart
| Depth | 1 cu yd covers | One 2 cu ft bag covers |
|---|---|---|
| 1 in | 324 sq ft | 24 sq ft |
| 2 in | 162 sq ft | 12 sq ft |
| 3 in | 108 sq ft | 8 sq ft |
| 4 in | 81 sq ft | 6 sq ft |
| 9 in (playground) | 36 sq ft | 2.7 sq ft |
Sources & assumptions
How this calculator gets its numbers. Full method: our methodology.
- Volume = bed area × depth; 27 cu ft = 1 cubic yard. Bags are 1.5, 2 or 3 cu ft and are rounded up.
- The default depth is 3 in. Extension guidance is that fine wood and bark mulches should be no more than 2–3 in deep and kept away from stems and trunks.
Sources
- Clemson Cooperative Extension, Home & Garden Information Center, Mulch (HGIC 1604). Recommended mulch depths and keeping mulch away from stems.
Last reviewed . Product figures vary by brand; the label on what you buy wins.
Frequently asked questions
How many bags of mulch do I need?
Multiply the bed area in square feet by the depth in inches, divide by 12 to get cubic feet, then divide by the bag size. For 200 sq ft at 3 inches you need 50 cubic feet, which is 25 bags of 2 cubic feet.
How much area does a 2 cubic foot bag of mulch cover?
About 12 square feet at 2 inches deep, 8 square feet at 3 inches or 6 square feet at 4 inches.
How many bags of mulch are in a yard?
13.5 bags of 2 cubic feet, 9 bags of 3 cubic feet or 18 bags of 1.5 cubic feet. One cubic yard is 27 cubic feet.
How deep should mulch be?
Two to three inches for most garden beds, three to four inches around trees and shrubs, and at least nine inches of wood mulch under playground equipment. Keep mulch pulled back from trunks and stems.
How do I calculate mulch for a circle or tree ring?
For a circle, area is 3.14 × radius squared. For a ring around a tree, subtract the trunk area from the ring area. A 6 ft ring around a 1 ft trunk is about 27.5 square feet, which needs about 3.4 bags of 2 cubic feet at 3 inches.
How much mulch do I need for a playground?
Multiply the play area by a depth of at least 9 inches. A 20 × 20 ft play area at 9 inches needs 300 cubic feet, or about 11.1 cubic yards. Bulk playground-grade wood fiber is usually the practical choice at that size.