Mulch formula
volume (cu ft) = length (ft) × width (ft) × (depth_inches ÷ 12). Bulk mulch is sold by the cubic yard (27 cu ft). Bagged mulch is usually 2 or 3 cubic feet. This calculator returns both so you can compare bulk delivery versus bags for small beds.
Worked example
A 20 × 5 ft bed at 3 inches needs 100 × 0.25 = 25 cu ft ≈ 0.93 cu yd, or thirteen 2 cu ft bags. At 2 inches the same bed needs about 16.7 cu ft—useful when refreshing an existing layer rather than starting bare soil.
| Bag | 2 in deep | 3 in deep | 4 in deep |
|---|---|---|---|
| 2 cu ft | 12 sq ft | 8 sq ft | 6 sq ft |
| 3 cu ft | 18 sq ft | 12 sq ft | 9 sq ft |
Depth guide (summary)
University extension guidance commonly recommends about 2–3 inches of organic mulch for shrub and perennial beds. Keep mulch a few inches away from tree trunks and woody stems. See our mulch depth guide and the tree ring mulch calculator for donut shapes.
Bulk vs bags
Bulk is usually cheaper above roughly one cubic yard and reduces plastic waste. Bags are convenient for rooftop beds, small townhouses, and topping up. Ask your yard whether the product is dyed, hardwood, pine bark, or composted—water needs and fade rates differ.
Common mistakes
- Volcano mulching against trunks.
- Ordering for the wrong depth after settling (fresh mulch compresses).
- Ignoring pathways that also need coverage.
Assumptions and limits
The mulch calculator results are planning estimates for rectangular or cylindrical shapes with uniform depth. Real sites have slopes, voids, and product variation. Always confirm coverage with the manufacturer label and local building practices before you buy large quantities.
Unit toggles switch input labels between US imperial and metric. Shareable URLs store your inputs in the query string for convenience, while the canonical tag stays on the clean page URL so search engines do not index every parameter combination.
Shopping checklist
- Write down the calculator outputs (volume, bags, or piece counts) and round up for waste.
- Call your supplier for density, dye lot, or delivery minimums when ordering bulk material.
- Check access for trucks, wheelbarrows, and staging space before delivery day.
- Photograph existing conditions so you can revisit dimensions if a helper measures differently.
FAQ
How much mulch do I need for 100 sq ft?
At 3 inches deep: 100 × 0.25 = 25 cu ft ≈ 0.93 cu yd, or thirteen 2 cu ft bags.
How many bags in a cubic yard of mulch?
A cubic yard is 27 cu ft, so 27÷2 = 13.5 of the common 2 cu ft bags (plan on 14 at the register) or nine 3 cu ft bags.
Related guides
Sources
- Iowa State Extension – How to determine amount of mulch needed Used for: Volume method (area × depth) for garden beds. Checked .
- UF/IFAS Gardening Solutions – Choosing and installing mulches Used for: Mulch depth and installation guidance. Checked .
- Mississippi State Extension – Mulches for the landscape Used for: Landscape mulch practice overview. Checked .
- Clemson HGIC – Mulch Used for: Extension mulch depth and care notes. Checked .
Estimates only—confirm bag yields on the product label and check local building codes before you pour or order. Not affiliated with QUIKRETE, Sakrete, Sonoco, or any manufacturer named in the sources. Found an error? Tell me.
Calculator version 1.0 · Changelog