How this calculator works. Volume = area × depth. We convert your bed's square footage and depth in inches to cubic feet (area × depth ÷ 12), then to cubic yards (÷ 27) — the unit bulk mulch is sold in.
Bag math uses the two standard retail sizes: 2 cu ft (most hardwood and dyed mulches) and 3 cu ft (typically pine bark). A cubic yard equals 13.5 two-cubic-foot bags.
How much mulch do I need?
The rule that answers almost every mulch question: one cubic yard covers about 100 square feet at 3 inches deep. Three inches is the sweet spot for new beds — thick enough to suppress weeds and hold moisture, thin enough not to suffocate roots. For an annual refresh over existing mulch, 1–2 inches is plenty.
Whether to buy bags or bulk comes down to quantity: below about 1.5 cubic yards, bags are easier to handle and often comparable in price; above that, a bulk delivery is significantly cheaper per yard — typically half the per-yard cost of bagged — though you'll need a spot for the pile and a wheelbarrow afternoon.
Coverage at common depths
| Depth | 1 cu yd covers | One 2 cu ft bag covers |
|---|---|---|
| 2 inches (refresh) | ≈160 sq ft | ≈12 sq ft |
| 3 inches (new bed) | ≈100 sq ft | ≈8 sq ft |
| 4 inches (paths, heavy weeds) | ≈80 sq ft | ≈6 sq ft |
Buying tips
Keep mulch 2–3 inches away from tree trunks and plant stems — "mulch volcanoes" rot bark and invite pests. If your beds are irregular, break them into rough rectangles and add the areas together, or pace the perimeter and estimate; mulch forgives imprecision better than tile does.
Common questions
Should I remove old mulch first?
Usually no. If the old layer is under 2 inches and not matted, fluff it with a rake and top up. Remove it only if it's moldy, compacted into a water-shedding mat, or already 3+ inches deep.
How many bags are in a cubic yard?
13.5 bags at 2 cu ft, or 9 bags at 3 cu ft. If your total approaches a yard, price out bulk delivery — it's usually much cheaper.
Does mulch type change the amount?
No — volume is volume. Type affects looks, longevity, and price: hardwood lasts 1–2 seasons, pine bark nuggets longer, dyed mulch holds color but check it's from clean wood.
What about landscape fabric underneath?
For beds with plants, skip it — fabric blocks water and organic matter, and weeds root on top of it anyway. A full 3-inch mulch layer controls weeds better.