Mulch Calculator
Enter your bed dimensions and how deep you want the mulch. You get cubic yards, the bag count if you are buying bagged, the weight for hauling, and what bulk delivery would save you.
The arithmetic
Mulch volume is area × depth. The only trick is unit conversion: depth is in inches, area is in square feet, and mulch is sold by the cubic yard.
Divide depth in inches by 12 to get feet, multiply by the area, then divide by 27 because a cubic yard is 27 cubic feet. The shortcut worth memorising: one cubic yard covers about 100 square feet at 3 inches deep.
How deep should it be
2 to 3 inches for topping up an established bed. Mulch decomposes from the bottom, so you are replacing what broke down, not starting over.
3 to 4 inches for a new bed or where you are trying to suppress weeds. Below about 2 inches, weeds come straight through and you have wasted the effort.
Never more than 4 inches, and keep it pulled back a few inches from trunks and stems. Piled mulch against bark holds moisture there, which invites rot and gives voles somewhere to work unseen. The "mulch volcano" around a tree is the single most common landscaping mistake, and it kills trees slowly enough that nobody connects the cause.
Fine-textured mulch should go on the shallow end of these ranges — it packs down and can shed water. Coarse nuggets can go deeper without matting.
Bagged versus bulk
Bags are convenient for small jobs and you can carry them in a car. Bulk is dramatically cheaper per unit — often less than half — and produces no plastic to dispose of.
The break-even is usually around two cubic yards, or roughly 27 bags. Below that, delivery fees eat the savings; above it, bulk wins clearly. The calculator shows both so you can see where your job falls.
If you go bulk, check the weight output before deciding to haul it yourself. A full-size pickup with an 8-foot bed holds about two cubic yards of mulch, which is fine — but the same truck cannot legally or safely carry two yards of soil or gravel, which weigh several times as much.
About the weight figure
The weights here are dry. Mulch soaked by rain can weigh 50% more or more, which matters if you are hauling it or wheeling it across a lawn. Order or pick up in dry weather when you can.
Frequently asked questions
How much does a cubic yard of mulch cover?
About 100 square feet at 3 inches deep, 160 square feet at 2 inches, or 80 square feet at 4 inches. A cubic yard is 27 cubic feet, so the coverage is simply 324 divided by the depth in inches.
How many bags of mulch are in a cubic yard?
Thirteen and a half bags at the standard US 2 cubic foot size, so you would buy 14. Smaller 0.8 cubic foot bags — common for rubber mulch and decorative stone — take about 34 to make a yard.
How deep should mulch be?
Two to three inches when topping up an established bed, three to four inches for a new bed or heavy weed pressure. Do not exceed four inches, and always keep mulch pulled back from tree trunks and plant stems, since piling it against bark traps moisture and causes rot.
Is bulk mulch cheaper than bags?
Usually much cheaper per cubic yard, often less than half the bagged price. The break-even including delivery is typically around two cubic yards, or about 27 standard bags. This calculator shows both totals for your specific job.
How much does mulch weigh?
Roughly 600 to 800 pounds per cubic yard for wood mulch when dry, and up to 1,500 pounds for rubber. Wet mulch can weigh 50% more. A full-size pickup handles about two cubic yards of wood mulch, but not two yards of soil or gravel, which are far heavier.