Mulch Calculator
Convert bed area and depth into cubic yards and bags of mulch, then compare bulk delivery against bagged prices to see which actually costs less.
Length × width; split odd shapes into rectangles.
3 in suppresses weeds; 2 in for refreshing an existing bed.
Bulk delivery saves about $36 here — the usual outcome past a yard or so. One cubic yard equals 13.5 bags.
The two-step everyone fumbles at the store
Mulch is sold in two incompatible units — 2-cubic-foot bags at the store and cubic yards from the landscape supplier — and standing in the parking lot converting between them is how people come home with eleven bags for a fourteen-bag bed. The conversion worth memorizing is that one yard is 13.5 bags; the calculator does the rest, including which price wins at your quantities.
Depth is a Goldilocks setting
The instinct that more mulch means fewer weeds fails at about the three-inch mark. Beyond it, mulch holds water against stems, invites rot and fungus, and starves roots of air — the infamous “mulch volcano” against a tree trunk kills trees slowly and confidently. Two inches refreshes; three suppresses; keep a bare ring around trunks; done.
Timing is the other half of the win — mulching after the soil warms but before summer locks in moisture is what the USDA’s backyard guidance gently calls conservation, and what your July water bill calls savings.
Bulk logistics, briefly
Bulk delivery drops a pile on your driveway, so the hidden inputs are a tarp, a wheelbarrow and an honest assessment of your weekend. A yard of mulch is manageable; the same yard of gravel weighs as much as a small car and should be dropped as close to its destination as the truck can reach — the same volume-times-density thinking the concrete calculator applies to the heaviest material of all.
How this is calculated
Volume (cu ft) = area × (depth in inches ÷ 12) Cubic yards = volume ÷ 27 Bags = volume ÷ 2 (standard 2-cu-ft bags)
Frequently asked questions
- How much mulch do I need?
- One cubic yard covers about 108 square feet at 3 inches deep, or 162 at 2 inches. Measure beds as rectangles, add them up, and pick a depth — 3 inches for weed suppression on new beds, 2 for an annual refresh over what survived the winter.
- Is bulk or bagged mulch cheaper?
- Bulk usually wins past a yard or so — one cubic yard equals 13.5 bags, and per-yard bulk pricing routinely runs 30 to 50 percent below the bag equivalent. Bags win on small jobs, colored-mulch matching, and not needing a truck or a tarp for the driveway.
- How deep should mulch be?
- Two to three inches. Less stops suppressing weeds; more suffocates roots and holds enough moisture against stems to cause rot. Deeper is not better — it is just heavier and worse.
- Does this work for gravel and compost?
- The volume math is identical — area times depth, sold by the cubic yard or bag. Only the weight changes, and dramatically — a yard of mulch runs 500-800 pounds while a yard of gravel runs about 2,800, which matters a great deal to whatever is hauling it.