Mulch Calculator: Cubic Yards for Your Garden Beds

Updated 2026-07-30 · Yardly

To mulch a set of garden beds, measure each bed’s square footage, multiply by the depth in feet (3 inches = 0.25), divide by 27 for cubic yards, and add the beds together before you order — a typical three-bed front yard totals 2 to 3 cubic yards. The per-bed worksheet below keeps the math honest.

Why beds get estimated wrong

A single rectangular bed is easy. Real yards aren’t: a curved border along the driveway, a kidney-shaped island, a ring around a maple, a row of raised beds. Eyeballing the whole yard as one blob is how people end up a yard short — or with a pallet of extra bags.

The fix is mechanical: treat every bed as its own line item, estimate it with the standard volume formula, then sum the column.

(Length × Width × Depth ÷ 12) ÷ 27 = cubic yards per bed

Depth goes in inches; the ÷ 12 turns it into feet, and the ÷ 27 turns cubic feet into cubic yards. The mulch calculator runs this per bed so you can add entries instead of juggling a notepad.

Measuring the awkward shapes

• Curved borders: measure the length along the curve, then take the width at three or four points and average them. Length × average width is close enough for mulch.
• Kidney and island beds: box them into a rectangle, estimate, and knock off 10–15% for the cut corners.
• Tree rings: radius × radius × 3.14. A ring 3 feet out from the trunk is about 28 sq ft — and leave a gap at the trunk (more below).
• L-shapes: split into two rectangles and estimate each.

When a shape makes you hesitate, round up. Leftover mulch tops up thin spots; a shortfall means a second delivery fee.

Depth depends on the mulch, not the bed

University extension guidance — see the University of Illinois Extension mulching guide — puts the working range at 2 to 4 inches, with the material deciding where you land:

• Fine or composted mulch (compost, shredded leaves, cocoa hulls): 2–3 inches. Fine textures mat when piled deeper, shedding water instead of passing it.
• Coarse bark and arborist wood chips: 3–4 inches. Big chunks leave air gaps, so they need more depth to suppress weeds.
• Refreshing an existing bed: measure what’s already there first. If 2 inches remain, you’re buying a 1-inch top-up — a third of the material, not a full re-do.

Around trees and shrubs, keep mulch pulled back a few inches from trunks and stems. Piling it against bark — the classic “mulch volcano” — traps moisture, softens bark, and invites decay and rodents.

A worked example: three beds, one order

Bed	Size	Depth	Cubic yards
Front foundation bed	24 × 5 ft	3 in	1.11
Curved driveway border	30 ft × 3 ft avg	3 in	0.83
Maple tree ring	3 ft radius (~28 sq ft)	3 in	0.26

Total: 2.2 cubic yards → order 2.5. At that quantity bulk delivery wins easily — 2.5 yards is 34 of the 2-cubic-foot bags.

One caution for vegetable and raised beds: mulch is a surface dressing, not a fill material. If you’re topping up the soil level inside a raised bed, that’s a soil-volume problem — the raised bed soil calculator handles it — and the soil calculator covers in-ground amendments. Mulch the surface only after the soil is where you want it.

Keep reading

• How much mulch do I need? covers the core formula, the 108-per-yard rule, and bagged-vs-bulk break-even.
• Filling planting beds first? Start with the raised bed soil calculator, then come back for the mulch layer.
• The landscape material calculators guide maps every Yardly tool to the right material.

Frequently asked questions