Depth by type of mulch
| Mulch | Depth | Source |
|---|---|---|
| Fine-textured wood or bark mulch | no more than 2–3 in | Clemson Extension[1] |
| Coarse mulch, such as pine bark nuggets | up to 4 in | Clemson Extension[1] |
| Grass clippings, shredded leaves | no more than 2 in | Clemson Extension[1] |
| Around trees | 2–3 in, not touching the trunk | Penn State Extension[2] |
| Around trees, maximum | 4 in (“no more than 2 to 4 inches”) | University of Vermont Extension[3] |
| Rubber mulch in landscape beds | at least 2 in | RubberLast (manufacturer)[4] |
Coarse mulch can go deeper because air still moves through it. Scotts recommends a 3 inch layer to keep weeds down,[5] which sits at the top of the range for fine mulch. If there is still mulch from last year, measure it and add only the difference.
Keep it off trunks and walls
- Trees. Keep mulch at least 3 inches from the root flare, where the trunk widens into the roots (UVM), or 2–3 inches from the stems of woody plants (Clemson).[3][1] Mulch piled against the trunk, the “mulch volcano,” holds moisture against the bark, invites rot and rodents, and encourages roots that circle and girdle the trunk.[2][3]
- Buildings. Clemson advises keeping mulch 6–12 inches from the walls of buildings, as a precaution against termites.[1]
How much mulch you need
One cubic yard covers 324 sq ft at 1 inch deep, so it covers 324 ÷ depth at any other depth.[1]
bags = cubic feet ÷ bag size, rounded up
cubic yards = cubic feet ÷ 27
Bagged mulch is usually sold in 2 cu ft bags, with some brands also in 1.5 cu ft.[5][6] For every 100 sq ft:
| Depth | Cubic feet | Cubic yards | 2 cu ft bags | 1.5 cu ft bags | 1 cu yd covers |
|---|---|---|---|---|---|
| 2 in | 16.67 | 0.62 | 9 | 12 | 162 sq ft |
| 3 in | 25.00 | 0.93 | 13 | 17 | 108 sq ft |
| 4 in | 33.33 | 1.23 | 17 | 23 | 81 sq ft |
One 2 cu ft bag covers 12 sq ft at 2 inches, 8 at 3 and 6 at 4. Rubber mulch comes in smaller bags: a 0.8 cu ft bag covers 4.8 sq ft at 2 inches, so 100 sq ft takes 21 bags.[7]
Example: a bed and a tree ring
- Bed 5 × 24 ft at 3 in: 5 × 24 × 3 ÷ 12 = 30 cu ft (1.11 cu yd) → 15 bags of 2 cu ft, or 20 of 1.5 cu ft
- Ring 6 ft across around a tree at 2 in: π × 3² × 2 ÷ 12 = 4.71 cu ft → 3 bags of 2 cu ft (a little less once you leave the gap at the trunk)
- Together: 34.71 cu ft → 18 bags of 2 cu ft or 1.29 cu yd in bulk
Bulk mulch weight
Shredded hardwood mulch weighs roughly 400–800 lb per cubic yard as delivered. That range is our estimate: the lab values are for oven-dried mulch (about 421 lb per cubic yard for shredded hardwood in NIST’s tests),[8] and a composting handbook gives 445–620 lb for wood chips without stating their moisture.[9] Delivered mulch is damp and heavier. A pickup bed usually fills before it reaches its payload with mulch; see truck capacity.
Questions people ask
What is the 3-3-3 rule for mulch?
It is a garden rule of thumb, and versions of it vary. The parts that match extension advice are a depth of about 3 inches (Penn State says 2–3 inches around trees) and a gap of at least 3 inches between the mulch and the root flare of a tree (University of Vermont).
How deep should mulch be around trees?
Two to three inches, spread wide and not touching the trunk (Penn State), and never more than 4 inches (University of Vermont). Leave at least 3 inches of bare ground around the root flare.
How far should mulch be from the house?
Clemson Extension advises keeping mulch 6–12 inches from the walls of buildings, as a precaution against termites.
Can you put down too much mulch?
Yes. Fine mulch deeper than 2–3 inches, or mulch piled against a trunk, holds moisture against the bark and can lead to rot and girdling roots. If last year’s layer is still there, top it up only to the recommended depth.
Related calculators and guides
Sources
- Clemson Cooperative Extension, HGIC 1604 Mulch. Depth by mulch type; keep mulch 6–12 in from buildings. Checked 2026-09-26.
- Penn State Extension, Mulch Volcanoes Are Erupting Everywhere!. Mulch 2–3 in deep; keep it off the trunk. Checked 2026-09-26.
- University of Vermont Extension, Beware the Mulch Volcano. Checked 2026-09-26.
- Mahantango Enterprises (RubberLast), Rubber mulch products. Rubber mulch about 26 lb per cubic foot; lay at least 2 in. Checked 2026-09-26.
- ScottsMiracle-Gro, Scotts Nature Scapes mulch, 2 cu ft. Checked 2026-09-26.
- Lowe’s (product listing), Timberline 2 cu ft black hardwood mulch. 2 cu ft bag; covers 12 sq ft at 2 in. Checked 2026-09-26.
- Lowe’s (product listing), Rubberific 0.8 cu ft rubber mulch. Checked 2026-09-26.
- NIST Fire Research Division, Suzuki and Manzello, bulk densities of landscape mulches. Checked 2026-09-26.
- Cornell Waste Management Institute / NRAES, On-Farm Composting Handbook, Appendix A Table 1. Bulk weights of wood chips, bark and leaves. Checked 2026-09-26.