How much mulch for a 3 ft × 40 ft foundation bed?
You need about 1.11 cubic yards of mulch (30 cubic feet) for a 3 × 40 ft bed along the house, 3 inches deep: 15 bags of 2 cu ft, or 10 bags of 3 cu ft.
How to work it out
- 40 ft × 3 ft = 120 sq ft
- 120 sq ft × 3 in ÷ 12 = 30 cu ft ÷ 27 = 1.11 cu yd
- 30 cu ft ÷ 2 cu ft per bag = 15 bags
- Bulk: 1.11 cu yd rounded up to the next ½ cu yd = 1.5 cu yd
Long, narrow beds against a foundation are easy to underestimate because 3 ft doesn’t sound like much — but 40 ft of it is 120 sq ft, more than a 10 × 10 bed. They also have rules the rest of the garden doesn’t: the house wall, the siding, the downspouts and the grade.
Adjust for your project
More options: Settling · Bag price · Bulk price …
- Mulch needed
- 1.11 cu yd (30 cu ft)
- If you order bulk, ask for
- 1.5 cu yd
- Area covered
- 120 sq ft
- Same job in the other common size: 10 bags of 3 cu ft (13.5 and 9 bags per cubic yard).
Mulch at 3 in for a 40 ft bed, by width
| Width | Mulch needed | Bags to buy |
|---|---|---|
| 2 ft | 0.74 cu yd | 10 bags |
| 3 ft | 1.11 cu yd | 15 bags |
| 4 ft | 1.48 cu yd | 20 bags |
| 5 ft | 1.85 cu yd | 25 bags |
| 6 ft | 2.22 cu yd | 30 bags |
What to know about a foundation bed
- Average the width. Foundation beds often curve out around shrubs. Measure the width every 10 ft and average it; a bed that runs 2–4 ft wide averages 3 ft.
- Keep it below the siding. Leave a few inches of bare foundation visible between the mulch and the bottom of the siding, and don’t bury vents or weep holes. Mulch against siding holds moisture there and hides what is going on at the wall.
- Keep the slope. The soil under the mulch should still fall away from the house. Mulch doesn’t fix a negative grade; add soil first if water pools against the wall.
- Downspouts and drip lines. Where roof water pours off, mulch washes out. A splash block, or a strip of stone under the drip line, works better — see How much river rock for a 3 ft strip along the house for the stone version of this same bed.
Fifteen 2 cu ft bags divide the 30 cubic feet exactly. If the front of the house has a matching bed on the other side of the door, that is 240 sq ft — double the order, or about the size of the How much mulch for a 10×20 area example.
Different size? Use the full Mulch Calculator.
What you’ll need
- Garden dump cartMid-range price
Easier than a wheelbarrow for hauling bags and pots, and it tips to unload. Check the rated load against what you will carry.
See options on Amazon (opens in a new tab) - Bow rake / landscape rakeBudget price
Steel tines for spreading gravel and soil and leveling it flat. The flat back of a bow rake doubles as a leveling tool.
See options on Amazon (opens in a new tab) - No-dig landscape edgingBudget price
Plastic edging pinned with spikes — keeps mulch in beds and grass out. Fine for mulch; too flimsy for gravel paths.
See options on Amazon (opens in a new tab)
As an Amazon Associate we earn from qualifying purchases. Links to products are affiliate links — they cost you nothing extra and help keep these calculators free.
Frequently asked questions
How much mulch for a 4 ft wide, 40 ft long bed along the house?
About 1.48 cubic yards at 3 inches deep, or 20 bags of 2 cu ft.
How much mulch to top up a 3×40 foundation bed by 2 inches?
About 0.74 cubic yards, or 10 bags of 2 cu ft.
Other common sizes
- How much mulch for a 10×10 area — 0.93 cu yd
- How much mulch for a 10×20 area — 1.85 cu yd
- How much mulch for a new 200 sq ft bed at 4 inches — 2.47 cu yd
- How much mulch for 1,000 sq ft — 9.26 cu yd
- How much mulch for a 6 ft tree ring — 4 bags
- How much mulch for 10 m² — 0.75 m³
Sources
- Penn State Extension — Mulching Landscape Trees (opens in a new tab) — 2–4 in of organic mulch and no more (less on poorly drained soil); keep it off the trunk; new mulch over old counts toward the depth.
- University of Minnesota Extension — Mulching for soil and garden health (opens in a new tab) — 2–4 in balances weed suppression with soil aeration.
- Colorado State University Extension — Mulching (opens in a new tab) — Wood chips and bark on the surface do not tie up soil nitrogen; mixing them into soil can.
- K-State Research and Extension, Johnson County — How to Mulch Trees (opens in a new tab) — Start mulch 3–6 in from the trunk and carry it out at least 3 ft in all directions; 6 ft is better.
- Messina’s — How much mulch fits in a truck bed? (opens in a new tab) — About 1.5 cu yd in a 5.5 ft pickup bed, about 2 in a 6.5 ft bed, 2.5–3 in an 8 ft bed.
- Harbor Soils — Cubic yard calculator and formula (opens in a new tab) — Topsoil and bark settle about 10% in the first season.
- Gravel Monkey — How many tons of gravel in a dump truck? (opens in a new tab) — Typical payloads: single-axle about 6–10 tons, tandem 12–16, tri-axle 18–25; gravel hits the weight limit before the bed is full.