15 × 20 ft bed: the short answer
At 3 inches deep, a 15 × 20 ft bed needs about 75.0 cubic feet of mulch — roughly 38 bags of 2 cu ft, or about 2.78 cubic yards in bulk.
Bed size
Mulch for a 15 × 20 ft bed
A 15 × 20 ft bed at 3 inches deep needs about 75.0 cubic feet of mulch — about 38 bags of 2 cu ft, or 2.78 cubic yards in bulk. Adjust depth and bag size below.
Mulch needed
—Enter bed size and depth to estimate mulch.
| Total volume | — |
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| Bulk (cubic yards) | — |
| Bags to buy | — |
| Coverage per bag | — |
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Shopping list
Run the calculator to prepare a list.
Estimate only.
Mulch is typically applied 2–3 inches deep (3–4 inches for weed suppression). Bag counts are
rounded up; coverage varies with how finely the mulch is shredded and how much it settles.
Before you buy
Mulch settles and breaks down, so topping up to 3 inches each year is normal rather than piling it deeper. For more than 8–10 bags, compare bulk delivery by the cubic yard.
Standard volume math at 3″ depth; 1 cu yd = 27 cu ft. Estimates only.
What a 15 × 20 ft bed usually needs
A 15 × 20 ft area is a large garden bed or a significant backyard mulching job. At 300 sq ft and 3 inches deep, the volume is about three-quarters of a cubic yard, which is the point where bulk delivery usually becomes the practical choice over dozens of bags.
How to decide
When the job reaches this size, quote bulk from a local landscape supplier and compare it with the bag path including tax and your time. Keep the 2–4 inch depth range from extension guidance in mind; deeper is not better if it piles against trunks or buries crowns. Order the calculated volume with a small overage for uneven ground.
Checks before you order
- Get a bulk quote and confirm the supplier's unit (cubic yard versus bag).
- Plan delivery access and where the pile can sit without blocking a driveway or drain.
- Leave clearance around tree trunks and shrub crowns regardless of bed depth.
FAQ
How much mulch for a 15 × 20 ft bed?
At 3 inches deep, a 15 × 20 ft bed needs about 75.0 cubic feet (2.78 cubic yards) of mulch — roughly 38 bags of 2 cu ft. Deeper mulch scales directly: 4 inches needs about a third more than 3 inches.
How many bags of mulch for a 15 × 20 ft bed?
About 38 bags of 2 cu ft at 3 inches deep. If that's more than 8–10 bags, price out bulk mulch by the cubic yard (2.78 cu yd here) — it's usually cheaper.
Sources & verification
Source links and page assumptions reviewed .
- University of Minnesota Extension: mulching for soil and garden health — Recommends 2–4 inches of mulch and keeping it clear of plant stems and trunks.
Estimate only, based on standard volume math at 3″ depth. Coverage varies with mulch type and settling; bag counts are rounded up. Confirm against your supplier before buying.