How Much Mulch Do I Need? A Simple Yard Calculator

Grab a tape measure and sketch your beds on paper. For a rectangular bed, multiply length by width. A bed 30 feet long and 4 feet deep is 120 square feet.

For a curved or irregular bed, break it into rough rectangles and add them up, or measure the length along the middle and multiply by the average width. For a circle around a tree, multiply the radius by itself and then by 3.14. A ring 4 feet out from the trunk is about 50 square feet.

Write down each bed and add the totals. Foundation beds, tree rings and the strip along the driveway add up faster than most people expect, so it pays to measure rather than guess.

For most landscape beds, 2 to 3 inches of mulch is the target, which matches the general guidance from UMass Extension and other horticulture programs. That depth holds moisture, keeps weeds down and moderates soil temperature without smothering plant roots.

If your beds already have a decent layer from last year, you usually only need to top dress with about 1 inch to restore color and bring the total back to 2 to 3 inches. Piling a full 3 inches on top of old mulch every year builds up a thick, matted layer that can shed water and starve roots of oxygen.

For new beds or bare soil, plan on the full 3 inches. Our clay and rocky MetroWest soils dry and crust in July and August, and a full layer makes a real difference.

Bulk mulch is sold by the cubic yard. Use this formula: square feet multiplied by depth in inches, divided by 324, equals cubic yards.

Example: 120 square feet at 3 inches deep is 120 times 3, which is 360. Divide by 324 and you get about 1.1 cubic yards. At 2 inches, the same bed needs about 0.75 cubic yards.

As a quick reference, one cubic yard of mulch covers about 324 square feet at 1 inch, about 162 square feet at 2 inches, and about 108 square feet at 3 inches.

Round up slightly. Mulch settles, beds are rarely perfect shapes, and a small extra amount is easier to deal with than coming up short in the middle of the job.

Bagged mulch at garden centers usually comes in 2 cubic foot bags. A cubic yard is 27 cubic feet, so it takes about 13.5 bags to equal one yard.

Bags make sense for small jobs: a single tree ring, a short walkway border or touching up a few thin spots. They are clean, easy to carry and you can store leftovers.

Bulk is usually the better value once you need more than about 2 yards. A typical MetroWest home with foundation beds, a few tree rings and a front walkway often needs somewhere in the range of 3 to 8 yards, and buying that many bags means a lot of plastic and a lot of trips.

Prices change by supplier, season and mulch type, so treat these as rough ranges. In MetroWest Massachusetts, bulk mulch typically runs roughly $35 to $65 per cubic yard for the material alone. Basic hemlock or dyed mulch tends to sit at the lower to middle end, and premium double ground bark or specialty blends at the higher end.

Delivery is usually extra. Many yards charge a flat delivery fee, often in the range of $50 to $100 or more depending on distance and load size, and some have a minimum order.

If you hire someone to install it, you are also paying for labor: weeding, edging, spreading and cleanup. That is why installed mulch is priced per job rather than just per yard. Procopio Landscaping & Design gives free estimates for mulch installation, with no visit fee, so you can compare the installed price against doing it yourself.

Weed first and cut a clean edge between the bed and the lawn. A crisp edge keeps mulch from washing into the grass and gives the whole yard a finished look.

Spread mulch evenly to the target depth. Keep it 3 to 6 inches away from tree trunks and a couple of inches away from shrub stems. Mulch piled against bark, often called a mulch volcano, holds moisture against the trunk and invites rot, insects and rodents.

Do not bury the crowns of perennials. Rake mulch around them, not over them.

In Massachusetts, the most popular time to mulch is mid to late spring, after the soil warms and spring cleanup is done. A fall refresh is also fine and helps insulate roots before winter, as long as you keep it at a normal depth.