How Much Mulch Do I Need?

The short answer

Multiply bed length × width × mulch depth in feet, then divide by 27. A 200 sq ft bed at 3 inches deep: (200 × 0.25) / 27 = 1.85 cubic yards — about 25 bags of 2 cu ft mulch, or 27–28 with 10% overage. For a fast estimate, divide square footage by 100 for a rough 3-inch figure in yards: 300 sq ft ≈ 2.78 yards.

Pick the right depth first

Depth is where most estimates go wrong. Use 2 inches when refreshing beds that already have mulch — you're topping up, not rebuilding. Use 3 inches for most new beds: enough to suppress weeds and hold moisture without smothering roots. Go to 4 inches only for coarse mulch or serious weed pressure. Keep mulch 3–6 inches away from trunks, stems, and siding — the infamous “mulch volcano” piled against bark rots it and invites pests. Measure existing mulch before adding more; the total shouldn't pass 4 inches.

Coverage: what one cubic yard buys you

Sanity-check your calculator result against this table before ordering. If the tool says 2 yards for a 216 sq ft bed at 3 inches, the table agrees (216 / 108 = 2).

Bags per cubic yard

One cubic yard is 27 cubic feet — divide 27 by the bag size:

Coverage per bag

Buying bags? Skip the yard math and work straight from the bag. Coverage per bag at common depths:

Example: a 10×10 bed (100 sq ft) at 3 inches needs 100 / 8 = 12.5 — call it 13 bags of 2 cu ft mulch, matching the FAQ math above. For 3 cu ft bags, the same bed needs 100 / 12 = 8.3, so 9 bags.

Bags vs bulk: the real math

Bulk mulch is usually cheaper once you pass about 2 to 3 cubic yards. A yard of bulk hardwood mulch often costs less than the 14 bags of 2 cu ft mulch that equal the same volume, and you skip hauling dozens of plastic bags. Bags win for small beds under 100 sq ft, touch-ups, and homes where a delivery truck can't reach. If delivery has a minimum (often 1 to 3 yards) or a delivery fee, compare the all-in totals before deciding. For a 1,000 sq ft bed at 3 inches — 9.26 yards, or 125 bags of 2 cu ft mulch — bulk delivery is the only sane choice.

Worked example: a 200 sq ft bed at 3 inches

Volume: (200 × 0.25) / 27 = 1.85 cubic yards. In 2 cu ft bags: 1.85 × 13.5 = 25 bags; round up and add 10% overage → 27–28 bags. Bulk route: order 2 yards (suppliers often sell whole yards) plus check the delivery minimum. Coverage check: 200 / 108 = 1.85 — the table agrees.

Common mistakes

Mulching too deep. More than 4 inches total can suffocate roots. Forgetting bed edges. Mulch migrates onto lawns and paths — a small overage covers the thin spots after the first rain. Ordering by bags for big beds. Do the bulk comparison once the number passes 2 yards. Measuring depth wrong. Depth is the finished layer, not how much you already have — subtract existing mulch first.