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How much mulch, and how deep

Mulch is the cheapest thing you can do for a tree and the easiest to overdo. The volume arithmetic is simple — square feet times inches, divided by 324 — and the depth is where almost every mistake happens.

Pre-filled with a realistic job. Change any input and the figure updates as you type — nothing is sent anywhere, and Print gives you a clean sheet without the buttons.

1.48 cu yd160 sq ft at 3.0 in
  • Area covered160.0 sq ft
  • Cubic feet40.0
  • Cubic yards to order1.48
  • Equivalent 2 cu ft bags20

Two to four inches, and not against the trunk

DepthEffectVerdict
1 inDries out, weeds throughToo thin to work
2–4 inHolds moisture, moderates soil temperature, suppresses weedsThe target
5–8 inExcludes oxygen, roots grow up into the mulchToo deep
Against the trunkBark stays wet, decay and girdling rootsActively harmful

Stop

The "mulch volcano" — a cone piled up the trunk — is the single most common tree-care mistake in the country. Mulch goes in a flat doughnut with the root flare visible.

Arborist chip is the good stuff, and it is usually free

Fresh arborist chip — the mixed wood, bark and leaf that comes out of a chipper — is excellent tree mulch and crews are frequently glad to drop a load rather than pay to tip it. Ask the crew on your street. Use it on beds and rings, not dug into planting holes, where the nitrogen draw of decomposing wood is a genuine problem.

If the chip is coming from your own stump grinding, size the mound with the grinding calculator — it estimates the cubic yards that job will leave.

The arithmetic, if you want to check it

Area in square feet, multiplied by depth in inches, divided by 324, gives cubic yards. The 324 is 27 cubic feet per cubic yard times 12 inches per foot. A standard bagged product is 2 cubic feet, so a cubic yard is thirteen and a half bags — which is why bulk delivery wins above about two yards.

Sources

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