Mulch Calculator

Enter your bed area and mulch depth to get cubic yards and bag counts, rounded up. Add a bag price and a bulk per-yard price and it also tells you which way is cheaper.

How much mulch you actually need

Mulch math is soil math: area times depth gives volume, and volume is what you buy — cubic yards in bulk, 2 or 3 cubic foot bags at the store. Depth is the decision that matters. 3 inches is the standard for a new bed: thick enough to block light to weed seeds and slow evaporation, thin enough that water and air still reach the soil. Refreshing a bed that already has mulch? 2 inches. And 4 inches is the ceiling, not a starting point — mulch deeper than that suffocates roots, holds soggy moisture against stems, and gives voles a highway. The "mulch volcano" piled against a tree trunk isn't a landscaping style; it's a slow way to kill the tree.

The formula

cu ft = area (sq ft) × (depth in inches ÷ 12) · cu yd = cu ft ÷ 27 · bags = cu ft ÷ bag size, rounded up

Coverage cheat sheet — one cubic yard covers 162 sq ft at 2″, 108 sq ft at 3″, and 81 sq ft at 4″. Bag shortcut: a yard is 13.5 two-cu-ft bags (call it 14) or 9 three-cu-ft bags, so you can sanity-check any store run in your head.

Worked example

A 12 × 18 ft planting bed (216 sq ft) at 3 inches: 216 × 0.25 = 54 cu ft = exactly 2 cu yd. That's 27 two-cu-ft bags or 18 three-cu-ft bags.

At $4.50 per 2 cu ft bag, bags run 27 × 4.50 = $121.50. Bulk at $38 per cubic yard is 2 × 38 = $76.00 — bulk saves $45.50 before delivery fees, which is why the cost comparison is worth filling in.

Bags vs bulk: where the flip happens

Per cubic foot, bagged mulch typically costs two to three times the bulk price — you're paying for plastic, pallets, and the privilege of loading 14 bags into a hatchback. Bulk flips the other way on small jobs, because delivery fees of $20-60 swamp the savings on a half-yard order. The practical rule: under about 1 cubic yard, buy bags; over about 1.5 yards, order bulk; in between, run both numbers (the calculator's comparison row does it for you, but remember to mentally add your supplier's delivery fee to the bulk side). One more bulk perk that never shows up in the math: no 27 empty plastic bags to throw away.

Frequently asked questions

How much area does a cubic yard of mulch cover?

At the standard 3-inch depth, one cubic yard covers 108 sq ft. At 2 inches it stretches to 162 sq ft, and at 4 inches it covers 81 sq ft. The math is simply 27 cubic feet divided by the depth in feet.

How deep should mulch be?

3 inches is the sweet spot for most beds — enough to suppress weeds and hold moisture. Use 2 inches for an annual refresh over existing mulch, and no more than 4 inches anywhere: deeper layers suffocate roots and keep soil soggy.

How many bags of mulch equal a cubic yard?

A cubic yard is 27 cubic feet, so it takes 13.5 of the common 2 cu ft bags (buy 14) or 9 of the 3 cu ft bags. If your project needs more than about a dozen bags, it's worth pricing bulk.

Is bulk mulch cheaper than bagged mulch?

Per cubic yard, bulk mulch usually costs half or less of the bagged equivalent — but delivery fees flip the math on small orders. Bags tend to win under about a yard; bulk wins beyond a yard and a half. Enter both prices above and the calculator compares them for your exact quantity.

Should mulch touch tree trunks?

No. Mulch piled against a trunk — the classic 'mulch volcano' — traps moisture on the bark, invites rot, insects, and girdling roots, and slowly kills the tree. Keep mulch 3-6 inches back from the trunk and shape it like a donut, not a volcano.