How I'd actually use this on a flip
The mulch order on a Chicago flip in 2022 went on the listing the day after spreading. Three cubic yards across four landscape beds out front and along the side yard — bagged, because the alley access wouldn't take a delivery truck. The math came back as 2.22 yd³ exact for the four beds combined; ordered 3.0 with the settling cushion. By the open house six weeks later the surface had compacted to roughly 2.25″ on a 3″ spread — exactly what the 25% cushion absorbs. If I'd ordered to the exact math, the mulch would have looked thin in the listing photos by week 6.
The other layer the math doesn't teach you is depth-by-target. Ornamental beds want 3″ for weed suppression + moisture retention. Vegetable beds want 1.5″ — shallow enough that the soil stays responsive to spring sun and rain. Tree rings get 3″ at the canopy edge but pulled BACK to the trunk flare — never piled against the bark. ANSI A300 (the arboriculture standard) and Penn State Extension agree on this: piling mulch against the trunk in a cone shape (volcano mulching) is what kills the tree. Most calculators won't tell you that.
On the supply side, mulch is one of the cleaner break-even decisions. Above 3 yd³ bulk is almost always cheaper per yard + you skip the bag-handling. Below 3 yd³ you're below the supplier's residential bulk minimum so bagged is usually the only option anyway. The 1-3 yd³ middle ground is where access matters: my 2022 alley couldn't take a truck, so even at 3 yd³ practical I went bagged — about 41 of the 2 cu ft bags, or 27 of the 3 cu ft.
Where this number breaks down
A few traps that put the math on the wrong side of the order:
- Volcano-mulching trees.ANSI A300 calls for mulch pulled 3-10″ away from the trunk depending on tree age. Piling above the trunk flare suffocates bark, traps moisture, and invites pest damage — it's how most newly-mulched trees die. The calculator's tree-ring mode renders a warning callout for a reason.
- Settling factor doesn't apply to refreshes. The 25% cushion compensates for fresh-mulch decompression in the first 6 weeks. If you're refreshing an already-settled bed where last year's mulch has already compacted, toggle the settling adjustment OFF — otherwise you'll over-order by a quarter-yard or two.
- Fine vs coarse coverage. Fine mulch (shredded bark, dyed) covers more area per cubic yard than coarse wood chips because it packs denser with less air. The calculator assumes coarse-yield conventions; fine mulch will cover ~10% more area at the same depth, but settles faster — net wash on the cushion.
- Vegetable beds want shallower. The 1.5″ default for vegetable mode is intentional. Above 2″ over a veg bed slows soil warming in spring + traps moisture against tender stems. Compost mulch is preferable to wood chips for vegetables anyway; the calculator math is the same but the material choice matters.
- Access can override the bulk-vs-bagged math.A 3 yd³ order that pencils to bulk delivery doesn't deliver if your alley or driveway can't take a truck. Plan the access before you commit to the cheaper-per-yard math.
Methodology
Every number on this page traces to one of three layers — site arithmetic for the volume math, manufacturer-conventional bag sizes (2 cu ft and 3 cu ft) for bag counts, and arboriculture + extension-service guidance for depth recommendations and tree protection. The per-cluster sourcing tier in methodology spells out which sources back which kinds of claims.
Show the formulas
- Volume:
(L ft × W ft) × (D″ / 12) / 27= cubic yards. - Practical order, with settling: exact × (1 + waste%/100) × 1.25, rounded UP to the next 0.25 yd³.
- Practical order, no settling: exact × (1 + waste%/100), rounded UP. Use for refreshing already- settled beds.
- Bag count, 2 cu ft:
ceil(practical × 13.5)— 13.5 bags / yd³. - Bag count, 3 cu ft:
ceil(practical × 9)— 9 bags / yd³.
Frequently asked
How much mulch do I need for 240 sq ft of beds at 3″ deep?
For 240 sq ft × 3″ deep — roughly four 60 sq ft landscape beds — the exact volume is 2.22 cubic yards (240 × 0.25 = 60 ft³, divided by 27). With the 5% waste cushion plus the 25% first-year settling adjustment (Penn State Extension: fresh wood-chip mulch loses 25-30% of its bulk volume in the first 6 weeks), that rounds up to 3.0 yd³ as the practical order. At 2 cu ft per bag that's 41 bags; at 3 cu ft per bag it's 27. Below the typical 3 yd³ supplier minimum so bagged is usually the cleaner call.
How thick should mulch be in a landscape bed?
2-4 inches is the sourced range — Penn State Extension recommends a 2-4″ layer for most ornamental beds and around landscape trees. Above 4″ the mulch traps too much moisture and starves roots; below 2″ it doesn't suppress weeds. SiteworkMath uses 3″ as the default for ornamental beds and tree rings, and 1.5″ for vegetable gardens where the shallower layer keeps soil temperature more responsive.
Why does the calculator add 25% on top of the waste cushion?
Fresh wood-chip mulch loses 25-30% of its bulk volume in the first 6 weeks as it compresses and the surface settles. Penn State Extension on mulching landscape trees calls out this settling explicitly. A 3″ application becomes 2-2.25″ by mid-summer; the 25% cushion gets you to next year's refresh without a midsummer top-up. Toggle the cushion off if you're refreshing an already-settled existing bed where the previous year's mulch has already compacted.
How many bags of mulch are in a yard?
13.5 bags at 2 cu ft per bag, or 9 bags at 3 cu ft per bag — the math is 27 ft³ (one cubic yard) divided by the bag size. Most retailers round up: a cubic yard of mulch is 14 of the 2 cu ft bags or 9 of the 3 cu ft bags. The calculator computes the exact ceiling for whichever bag size you select.
Should I volcano-mulch my trees?
No — and most calculators won't tell you that. Piling mulch in a cone shape against the trunk traps moisture, rots bark, and invites pest damage. ANSI A300 (the arboriculture standard) calls for 2-4″ of mulch at the canopy edge with the mulch pulled 3-10″ away from the trunk depending on tree age. Penn State Extension's 3-3-3 rule is the easy-to-remember version: 3″ deep, 3″ away from the trunk, in a 3-foot-wide ring. The calculator's 'Tree ring' mode renders a warning when selected.
Should I use bagged or bulk mulch?
Above 3 cubic yards, bulk delivery is almost always cheaper than bagged on a per-yard basis — but you're trading a Saturday's worth of bag handling for a Saturday's worth of wheelbarrow runs. Below 3 yd³, most Chicago-suburb suppliers won't bulk-deliver without a short-load fee, so bagged is usually the only practical option. The awkward middle is 1-3 yd³, where bulk is cheaper per yard but the supplier minimum forces you to bagged or to a smaller-minimum supplier. The calculator flags this with a 'below bulk minimum' status.
Related guides
- How much mulch for my garden bed →
- How much mulch is in a yard →
- Square yard vs cubic yard →
- How much mulch is in a cubic yard →
By James Wu. Volume math is site arithmetic, formulas shown above. Mulch depth recommendations + tree protection from Penn State Extension — Mulching Landscape Trees (the 2-4″ depth range, the 3-3-3 rule, the trunk-distance guidance). Arboriculture standard via ANSI A300 (Tree Care Industry Association) for the formal 2-4″ depth specification + the volcano-mulching prohibition. Tree-protection cross-check from Iowa State Extension — Mulch Depth Around Trees and Shrubs. Settling adjustment (~25% bulk volume loss in first 6 weeks) tracks Penn State Extension on landscape-tree mulching. Engine logic in lib/sitework/mulch.ts. Not arboriculture advice — for tree-care decisions specific to your trees, work with an ISA-certified arborist. Full methodology.