How much mulch do I need?
Mulch is bought by volume and spread by depth, so the whole calculation is area × depth, converted to the units the store sells in. The garden-center unit is the cubic yard (27 cubic feet); the bag is 2 or 3 cubic feet. Everything else on this page is deciding the depth and the cheaper way to buy.
The 324 is 12 inches per foot × 27 cubic feet per yard. A 200 sq ft bed at 3 in is 1.85 cubic yards — 25 two-cubic-foot bags or 17 three-cubic-foot bags. One cubic yard covers 108 sq ft at 3 in.
How many bags of mulch in a cubic yard?
14 two-cubic-foot bags (13½, so round up), 9 three-cubic-foot bags, or 18 of the 1.5 cu ft bags. That ratio is why bagged mulch looks cheap by the bag and isn't by the yard: a $4 bag of 2 cu ft is $54 per cubic yard, against $30–45 for the same material loose.
| Bed (at 3 in) | Cubic yards | 2 cu ft bags | 3 cu ft bags |
|---|---|---|---|
| 50 sq ft | 0.46 | 7 | 5 |
| 100 sq ft | 0.93 | 13 | 9 |
| 200 sq ft | 1.85 | 25 | 17 |
| 400 sq ft | 3.70 | 50 | 34 |
| 800 sq ft | 7.41 | 100 | 67 |
Bags rounded up. No waste factor — mulch is raked to fit; order the next bag or half-yard up if you like a margin.
Bulk vs bagged: where's the crossover?
Bags win on small jobs because bulk comes with a delivery fee; bulk wins on big jobs because the per-yard price is a third of bagged. The crossover is just the delivery fee divided by the per-yard price gap, and the calculator prints it for your two prices. With typical numbers it's 2–4 yards — roughly a 200–400 sq ft bed at 3 in.
Bags at $4 for 2 cu ft ($54 per yard) versus bulk at $35 per yard plus $60 delivery: bulk starts winning at 3.2 cubic yards. One yard costs $56 in bags and $95 delivered — buy bags. Four yards costs $216 in bags (54 of them) and $200 delivered — buy bulk and save $16. Prices are illustrative; enter yours above.
Two things the arithmetic doesn't show: bulk mulch is loose and arrives in a pile on your driveway, so budget the wheelbarrow time; and bags can be bought one at a time as you go, which matters if you're not sure of the area. If you have a truck, picking up bulk yourself removes the delivery fee and moves the crossover to zero — a half-ton short bed holds about 1.5 yards of mulch, a long bed 2.
How deep should mulch be?
Deep enough to block light to weed seeds and hold moisture, shallow enough that water and air still reach the soil — which for most bark and wood mulches means 2–3 inches settled, up to 4 for coarse chips, and much less for fine materials. Topping up an existing bed needs only what's decayed, usually 1–1½ inches. More is not better: mulch piled 5–6 in deep stays wet, sours, and roots grow up into it.
| Material | Depth | Weight per cu yd | Notes |
|---|---|---|---|
| Shredded hardwood / bark mulch | 2–3 in | 400–800 lb | The default bed mulch. 3 in for a new bed, 1–2 in to top up. |
| Wood chips / arborist chips | 3–4 in | 500–800 lb | Coarse; goes deeper without smothering. Often free from tree crews. |
| Cedar / cypress mulch | 2–3 in | 400–600 lb | Light, slow to break down, insect-resistant reputation. |
| Pine bark nuggets | 2–3 in | 400–600 lb | Floats and migrates in heavy rain; not for slopes. |
| Compost (as mulch or topdressing) | 1–2 in | 1,000–1,600 lb | Feeds the bed; thin layers. Heavy when wet. |
| Rubber mulch | 1.5–2 in | 600–900 lb | Doesn’t decay; holds heat; playgrounds more than beds. |
| Decorative stone / river rock | 2–3 in | 2,400–2,900 lb | Permanent; needs fabric underneath; order by the ton. |
Typical ranges from extension mulch fact sheets and supplier specifications. Weight depends mostly on moisture — a wet yard of hardwood mulch is nearly twice a dry one.
Coverage chart
| Depth | 1 cu yd covers | 2 cu ft bag covers | 3 cu ft bag covers |
|---|---|---|---|
| 1 in | 324 sq ft | 24 sq ft | 36 sq ft |
| 2 in | 162 sq ft | 12 sq ft | 18 sq ft |
| 3 in | 108 sq ft | 8 sq ft | 12 sq ft |
| 4 in | 81 sq ft | 6 sq ft | 9 sq ft |
Coverage = volume × 12 ÷ depth. The bag's printed coverage is usually the 2 in figure — check which depth it assumes.
Weight, and whether your truck can take it
A cubic yard of bark mulch weighs 400–800 lb depending on how wet it is; a yard of compost or stone is two to six times that. The calculator prints the range for the material you chose so you know whether it's a couple of pickup trips or a delivery. Most garden centers will load a pickup by the half-yard with a bucket loader; tell them what you drive.
Keep it off the trunks
Mulch against a tree trunk or a foundation — the "mulch volcano" — holds moisture against bark and siding, invites rot and insects, and in the case of the trunk can slowly kill the tree. Pull it back a few inches from stems and trunks, and keep it below the siding line. Same volume, better shape.
Sources: Clemson HGIC 1604, Mulch; University of Minnesota Extension, Mulching and watering; Penn State Extension, Mulching Landscape Trees. Bag sizes and bulk units as sold by US garden centers; weights from supplier published specifications.