Mulch Calculator
Work out cubic yards and bag counts for any bed, circle, or tree ring at your chosen depth — before you haul a single bag you didn't need.
For odd-shaped beds, split them into rectangles and add them up.
Keep mulch 3–6″ off the trunk — no “mulch volcanoes.”
More than 4″ suffocates roots and invites pests.
You need
Enter dimensions
| Bagged mulch | Bags needed |
|---|---|
| 2 cu ft bags (most common) | — |
| 3 cu ft bags | — |
| 1.5 cu ft bags | — |
Bulk mulch commonly runs $30–$60 per yard; delivery may be extra.
How to Calculate Mulch
Mulch is sold by volume — bulk by the cubic yard (27 cubic feet), bagged most commonly in 2 cu ft bags. Three steps:
- Find the bed area in square feet (length × width, or π × radius² for circles).
- Multiply by depth in feet. 3 inches = 0.25 ft.
- Divide by 27 to get cubic yards, or by the bag size to get bags.
Mulch formulas
Rectangular bed: volume = length × width × depth
Circular bed: volume = π × (diameter ÷ 2)² × depth
Tree ring: volume = (outer circle − trunk circle) × depth
Worked example — 12 × 4 ft bed at 3″: 48 sq ft × 0.25 ft = 12 cu ft → 0.44 cubic yards, or 6 bags of 2 cu ft mulch.
Mulch Coverage Per Yard and Per Bag
| Depth | 1 cubic yard covers | One 2 cu ft bag covers |
|---|---|---|
| 2″ | 162 sq ft | 12 sq ft |
| 3″ | 108 sq ft | 8 sq ft |
| 4″ | 81 sq ft | 6 sq ft |
Quick rule: divide 324 by depth in inches to get square feet covered per cubic yard.
Bulk vs. Bagged Mulch
- Around 10+ bags (¾ yard), bulk usually wins on price. A yard bulk is $30–$60; the same volume bagged is 13.5 bags at $3–$6 each.
- Bags win on logistics — no pile on the driveway, no rush to spread, easy to store extras, and colored mulches are more consistent bagged.
- Check delivery fees. A $25–$50 delivery charge can erase bulk savings on small orders — many yards deliver free above 2–3 yards.
Tips Before You Spread
- Edge first. A clean trench edge keeps mulch in the bed and makes any amount look professional.
- Weed and water before mulching — mulch locks in the moisture conditions underneath it.
- Keep it off trunks and stems. 3–6 inches of clearance prevents rot and rodent damage.
- Top up, don't pile up. Fluff last year's layer and add only enough to return to 3 inches total.
Frequently Asked Questions
How many bags of mulch in a cubic yard?
13.5 of the common 2 cu ft bags, or 9 of the 3 cu ft bags — a cubic yard is 27 cubic feet.
How deep should mulch be?
2–4 inches; 3 is the standard target. More than 4 suffocates roots. Keep it a few inches off trunks and stems.
How much does a yard of mulch cover?
108 sq ft at 3 inches deep; 162 at 2 inches; 81 at 4 inches. Divide 324 by depth in inches.
Do I remove old mulch first?
Usually no — rake it, fluff it, and top up. Remove it only if matted or moldy. Topping up takes about half the material of a fresh install.
How much mulch around a tree?
A 6 ft wide ring at 3 inches deep takes about 7 cu ft — three to four 2 cu ft bags — leaving a bare circle at the trunk.
Is bulk or bagged cheaper?
Bulk, once you pass roughly 10 bags of volume — unless delivery fees close the gap. Bags win for small jobs and storage.
References
- University of Minnesota Extension — mulching landscape plants (depth guidance): extension.umn.edu
- Texas A&M AgriLife Extension — mulch benefits and application: agrilifeextension.tamu.edu
- ISA / Arbor Day Foundation — proper tree mulching (no mulch volcanoes): arborday.org