How Much Mulch for 400 Square Feet?
Material needed
3.7 cubic yards
400 square feet at 3 inches deep, bark mulch at roughly 800 lb per cubic yard.
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How that number is worked out
These are the figures this page was built with and every line the calculator produces from them. Change anything above and all of it moves.
- Bed area400 sq ft
- Depth3 in
- MaterialMulch
Material needed3.7 cubic yards
| Volume | 100 cu ft |
|---|---|
| Cubic yards | 3.7most yards sell in half yard steps |
| Order in half yards | 4 cu yd |
| 2 cu ft bags, if bagging it | 50 |
| Approximate weight | 2,963 lb (1.48 tons) |
The material list this produces
| Material, cubic yards | 4 |
|---|---|
| Landscape fabric, sq ft | 400 |
| Edging, linear ft | 80 |
Depth compared
Depth is the whole calculation. Two inches will not suppress weeds, six inches will suffocate roots.
| Depth | Material needed | Order in half yards |
|---|---|---|
| 2 in | 2.47 cubic yards | 2.5 cu yd |
| 3 in | 3.7 cubic yards | 4 cu yd |
| 4 in | 4.94 cubic yards | 5 cu yd |
| 6 in | 7.41 cubic yards | 7.5 cu yd |
What else matters here
Four yards is the answer for a first mulching, when there is bare soil and the full three inches has to go down. It is not the answer for next year.
Mulch does not get removed before it is refreshed. Last year's layer is still there, part rotted, and topping up to depth takes an inch or an inch and a half, not three. On this bed that is a two yard order instead of a four yard one, every year after the first.
Piling a fresh three inches on top of the old every spring is how beds end up with six or eight inches of mulch against the stems. That layer sheds water rather than absorbing it, keeps the crown wet, and is a common way to lose established shrubs slowly enough that nobody blames the mulch.
What this calculator assumes
- Three inches is the usual mulch depth. Two is thin and will not hold weeds down, four starts to smother shallow roots and holds water against trunks.
- Weights are approximate and vary with moisture: mulch about 800 lb per cubic yard, topsoil 2200, gravel 2800, sand 2700.
- Bagged material is sold in 2 cubic foot bags, and there are 13.5 of those in a cubic yard.
Questions people ask
How many yards of mulch for 400 square feet?
About 3.7 cubic yards at 3 inches deep, ordered as 4 yards for a first application.
How much mulch to refresh 400 square feet?
Around 2 yards. Topping up an existing bed needs an inch to an inch and a half, not the full three, because last year's layer has not gone anywhere.
Can you put too much mulch down?
Yes. Past four inches it sheds water instead of holding it and keeps stems and crowns permanently damp. Piling fresh mulch on old every year is the usual cause.
The mulch and gravel calculator takes any dimensions you like and hands back the same list.