Mulch calculator: how many yards or bags do you need?

New beds with weeds to smother need 3–4 in. A cubic yard is 13½ bags of 2 cu ft — roughly a compact pickup bed filled level, or 5–6 wheelbarrow loads. Add your bag price, bulk price and delivery fee (under More options) to see which way is actually cheaper for this job.

How the mulch calculator works

Mulch is sold by volume, so the math is area × depth. Work the bed out in square feet, multiply by the depth in feet (inches ÷ 12), and you have cubic feet. Bulk suppliers sell by the cubic yard, which is 27 cubic feet — a box 3 ft on each side.

cubic feet = length (ft) × width (ft) × depth (in) ÷ 12
cubic yards = cubic feet ÷ 27
bags = cubic feet ÷ bag size (cu ft)
circle area = 3.1416 × (diameter ÷ 2)²
triangle area = base × height ÷ 2

A cubic yard fills 13.5 bags of 2 cu ft or 9 bags of 3 cu ft. In metric, 1 m³ is 1,000 litres, so it fills 20 bags of 50 L. The result starts with a plain shopping list: the bag count, and from about a yard up, the exact phrase to use when you call a landscape yard.

How deep should mulch be?

Penn State Extension’s mulching guide also points out that new mulch spread over old in successive years is the same as spreading too deep a layer at once — so measure what is already there before you buy. For tree rings, K-State Research and Extension suggests starting the mulch a few inches from the trunk and carrying it out at least 3 ft in every direction, farther if you can.

Measuring odd-shaped beds

Few beds are neat rectangles. Pick Curvy bed and enter the length plus a few widths (add as many as the bed needs), or break the bed into rectangles, a circle and a corner triangle, run each one and press Add to project list — the list totals the yards, bags and cost for you, and adds a rounded bulk-order line. Several identical tree rings? Pick the circle and set How many of these. A 10–15% overestimate is harmless; running out halfway through a Saturday is not.

Worked examples by size

The common sizes are already worked out, each with its own quirks: a small How much mulch for a 10×10 area bed that fits in the car, a How much mulch for a 10×20 area planting where bulk starts to make sense, and a How much mulch for a 3×40 ft foundation bed strip along the house. For whole-yard jobs see How much mulch for 500 sq ft and How much mulch for 1,000 sq ft; for a first-year bed, How much mulch for a new 200 sq ft bed at 4 inches; for trees, How much mulch for a 6 ft tree ring; and in metric, How much mulch for 10 m².

Bags or bulk: where the break-even usually falls

Enter both prices and a delivery fee under More options and the calculator tells you which is cheaper for your job. Landscape yards generally sell in half- or whole-yard steps (0.5 or 1 m³ in metric), so the bulk cost is worked out on the rounded-up order, not the exact volume. If the yard has a minimum delivery, enter it too: below the minimum you pay for the minimum (or a short-load fee), and the calculator says how much will be left over. As a rough pattern, bags tend to win below about a yard (no delivery fee, no leftover pile), and bulk tends to win somewhere past two or three yards — but local prices and delivery charges move that line a lot.

Practical tips

• Check how much old mulch is left before buying. If there is 1–2 in still there, you only need to top up to 3 in.
• Keep mulch off tree trunks and plant stems. Piled against bark ("volcano mulching"), it holds moisture where you don’t want it.
• Bagged mulch is compressed and fluffs up a little; bulk mulch settles after the first rain. The estimate assumes no settling; if you want the bed to look full all summer, add 5–10% under Extra for settling.
• Wood mulch left on the surface doesn’t rob your plants of nitrogen — Colorado State University Extension notes the tie-up happens when wood chips are mixed into the soil, not laid on top.
• Past roughly 3 cubic yards, bulk delivery is usually worth pricing out — but compare the delivered price, not the per-yard price.

For coverage per yard and per bag at every depth, see the mulch coverage chart, and for the money side, bagged vs bulk mulch. New to terms like bulk and cubic yard? See words you’ll hear at the yard. Using pine needles instead? The pine straw calculator works in bales.