How much mulch do I need?
Working out how much mulch to buy comes down to one thing: the volume of the bed you're covering. Measure the bed, choose a depth, multiply them together, then convert that volume into the unit your supplier sells by — cubic yards for bulk, or bags.
Buying bagged mulch? Most bags hold 2 cubic feet, so one cubic yard is about 13.5 bags. The calculator above does all of this the instant you type — switch Sold by to Bag and it rounds up to whole bags.
Rectangle or circle
For a rectangular bed — along a fence, path, or foundation — the area is simply length × width. For a round bed like a tree ring or island, it's π × radius². Pick the shape at the top of the calculator and the right measurement boxes appear.
Worked example
A rectangular bed 20 ft long and 4 ft wide, covered 3 inches deep:
20 × 4 × 0.25 ÷ 27 = 0.74 cubic yards, or about 10 bags of 2 cu ft each. Add ~10% for settling and round up when ordering.
How deep should mulch be?
- 1 inch — top-dressing an existing mulch layer
- 2–3 inches — the sweet spot for most beds
- 3–4 inches — stronger weed suppression and moisture retention
Keep mulch a few inches clear of trunks and stems — piling it against them (a "mulch volcano") traps moisture and invites rot. Tap a depth chip in the calculator to drop in a common depth without typing.
Coverage per cubic yard
One cubic yard of mulch spreads across a surprising amount of ground — how far depends entirely on depth:
| Depth | Coverage / yd³ |
|---|---|
| 1 inch | 324 sq ft |
| 2 inches | 162 sq ft |
| 3 inches | 108 sq ft |
| 4 inches | 81 sq ft |
Prefer bags? At 2 cubic feet each, one bag covers about 8 sq ft at 3 inches deep. Switch Sold by to Bag and set your bag size — the calculator rounds up to whole bags.
Common questions
How much mulch do I need?
Multiply your bed area by the depth to get a volume, then convert to cubic yards or bags. For a rectangle, area is length × width; for a circle it's π × radius². Multiply by depth in feet and divide by 27 to get cubic yards. The calculator above does all of this instantly as you type.
How many bags of mulch are in a cubic yard?
A cubic yard is 27 cubic feet. Bagged mulch is most often sold in 2 cubic foot bags, so one cubic yard equals about 13.5 of those bags. If your bags are a different size, set the bag size in the calculator and it rounds up to whole bags for you.
How deep should mulch be?
For most beds, 2–3 inches is ideal. Use about 3–4 inches to suppress weeds more strongly, and as little as 1 inch when simply top-dressing an existing layer. Keep mulch a few inches clear of trunks and stems. Tap a depth chip in the calculator to use one of these.
Should I order extra mulch for waste?
A little. Mulch settles and beds are rarely perfectly even, so adding about 10% is a sensible buffer. Tap “+ Add waste calc” in the project total to add a percentage to your order.
Does this mulch calculator work in metric?
Yes. Switch to "Metric" to enter your bed in metres and depth in centimetres. The result is shown in cubic metres or bags, so you can order in whichever unit your supplier uses.