Mulch Calculator (Yards)

How many yards of mulch do I need?

600 sq ft of beds at 3 inches deep needs 5.6 cubic yards - or 76 two-cubic-foot bags, which is the comparison that sends people to bulk delivery. At $40/yard bulk vs ~$4/bag, the same mulch costs $225 delivered loose or $300+ bagged, and the yard math (area × depth ÷ 324 for inches-to-yards) is exactly what this calculator runs.

Depth: the 3-inch sweet spot

Under 2" barely suppresses weeds; over 4" suffocates roots and sheds water instead of passing it. Refreshing annually? Rake the old layer first and top with 1–2" - mulch stacked yearly to 6"+ is a slow plant killer. And never against trunks: the "mulch volcano" holds moisture on bark, inviting rot and borers.

Which mulch

Shredded hardwood knits together on slopes; bark nuggets last longer but float and roll; dyed mulches hold color but check for CCA-free sourcing; cedar resists insects. Around vegetables, use straw or untreated wood. Stone is forever but hot - different calculator problem (density: use the gravel calculator).

Circular beds and tree rings

Rectangular area × depth doesn't work for a ring around a trunk - that's a circle, and the formula is πr² minus the trunk's own footprint, run through the same inches-to-yards conversion. A 5-ft-radius ring (10-ft circle) is π × 5² = 78.5 sq ft; at 3" deep, 78.5 × 0.25 ÷ 27 = 0.73 cubic yards, about 10 two-cu-ft bags. Double the radius to 10 ft and the area quadruples to 314 sq ft - not double - because area scales with the square of the radius, so eyeballing "twice as wide, twice the mulch" on tree rings under-orders badly. For a donut bed with an open paver or grass circle left in the middle, subtract that inner circle's area (πr_inner²) before converting to yards, or the number comes in high.

Truck bed limits and delivery minimums

Bulk pricing assumes you can get the mulch home. A full-size pickup bed holds roughly 2 to 2.5 cubic yards heaped before it spills on the drive - past that, it's a second trip or paying for delivery. Delivery usually carries a flat fee, and many yards set a minimum order below which they won't dispatch a truck at all. Run a 1.5-yard order at $40/yard: $60 for the mulch, but well over $100 once a flat delivery charge is added - at that point 20 two-cu-ft bags at roughly $4 each undercuts bulk even though the per-yard bulk price looked cheaper on paper. The bulk-beats-bags line only holds once volume clears the delivery fee, not just the one-yard mark.

Buffering for waste and uneven ground

Beds measure as clean rectangles on paper but rarely spread that way. Curves, root flare, edging stones, and slopes all eat into coverage without changing the length × width number, so build in a buffer - the trade's common rule of thumb is around 10% - on any bed that isn't a flat, obstacle-free rectangle. Running short mid-spread costs more than getting it right the first time - a second, partial-yard bulk order often carries the same flat delivery fee as the first, or forces a bag run at retail price to finish a few square feet. On sloped beds, mulch also migrates downhill over a season regardless of starting depth, so weight the extra toward the uphill third of the slope instead of adding depth evenly across the whole bed.

Related tools

Build the bed first: topsoil calculator. Lawn beside it: sod or seed. Landscapers: quote spreading via job costing.