How much mulch do I need for a 20 × 10 ft bed, 3 inches deep?
For the worked example (20 × 10 ft bed, 3 in deep) the material list is Mulch: 25 × 2 cu ft bags (calculated 25 bags, based on 3 in deep, no allowance). Quantities to buy are whole units rounded up from the calculated amounts. Enter your own measurements in the calculator above for your exact list.
How to use this calculator
- Measure the bed length and width, or enter the area if you already know it.
- Set the depth. 3 inches is an editable starting value.
- Pick the bag size on the bags you will actually buy, or enter a custom size.
- Use the bag count, or the cubic yards if you are buying bulk.
- Copy, print or share the material list.
How this is calculated
- Area (sq ft) = length × width
- Cubic feet = area × depth (inches) ÷ 12
- Cubic yards = cubic feet ÷ 27
- Bags = round up (cubic feet ÷ cubic feet per bag)
Geometry is deterministic. Material coverage, density, installation waste and product yield can vary. We expose those assumptions so you can replace them with the values printed on the products you are actually buying. Treat every result as an estimate. Items on your list are labelled Calculated (straight from your measurements) or Estimated (depends on an assumption), and “Buy” quantities are whole units rounded up.
Sources
No third-party figure is built into this calculator. Quantities come from geometry and from the values you can see and edit under “Assumptions” below, each labelled by where it comes from.
Last reviewed: . See the methodology.
Assumptions
These starting values are used until you change them. They are typical, not universal. Check the label on the product you are buying.
| Assumption | Starting value | Where it comes from |
|---|---|---|
| Cubic feet in a cubic yard | 27 | Mathematical – 3 ft × 3 ft × 3 ft |
| Inches in a foot | 12 | Mathematical – Depth in inches ÷ 12 gives feet |
| Default depth | 3 in | Common planning default – An editable starting value, not horticultural advice. |
| Mulch depth | 3 in | Common planning default |
| Custom bag size | You enter it | You enter it (product / supplier) |
| Extra allowance | 0% | Common planning default |
Worked example
A 20 × 10 ft bed, mulched 3 in deep, using 2 cu ft bags:
- Mulch: 25 × 2 cu ft bags (50 cu ft needed, or 1.85 yd³ in bulk) · 3 in deep, no allowance
Common questions
How deep should mulch be?
Common mulch depth is roughly 2–4 inches, but the right depth depends on the type of mulch and the plants, so treat the 3 in default as an editable starting value, not horticultural advice.
Does it add extra for waste?
Not unless you choose to. The extra allowance starts at 0%.
My store sells different bag sizes.
Pick “Custom” and enter the size printed on the bag.
Guides
- How Much Mulch Do I Need?Bed area and depth turned into bags or cubic yards of mulch.
- How Mulch Depth Changes How Much You NeedSame bed at 2, 3 and 4 inches: how depth scales the quantity.
- How Much Topsoil Do I Need?Area and depth turned into cubic yards or bags of topsoil.
- How Much Soil Do I Need for a Raised Garden Bed?Length, width and fill depth, bed by bed, in yards and bags.
- How Much Landscape Fabric Do I Need?Strips, overlap and whole strips per roll, not just area divided by roll area.