A 20 × 8 ft border, 3 in deep
Rectangle, length 20 ft, width 8 ft, depth 3 in, bag size 2 ft³.
Mulch needed, including waste
1.63 cubic yards
- Total volume (incl. 10% waste): 1.63 yd³ (44 ft³)
- Bags (2 ft³ each): 22
Mulch Calculator
This mulch calculator shows how much mulch you need for a rectangular or round garden bed at the depth you choose, in cubic yards or cubic metres, plus the number of bags.
Last updated
How much mulch do I need for a 20 × 8 ft bed at 3 inches deep?
About 1.63 yd³ including 10% extra. That is 22 bags of 2 cubic feet, or a 1.75 yd³ bulk delivery.
Mulch needed, including waste
1.63 cubic yards
- Area covered
- 160 ft²
- Base volume
- 1.48 yd³
- Total volume (incl. 10% waste)
- 1.63 yd³ (44 ft³)
- Bags (2 ft³ each)
- 22
- Recommended bulk orderBulk delivery is usually cheaper than bags for larger beds.
- 1.75 yd³
Inputs
- Bed shape: Rectangle
- Length: 20 ft
- Width: 8 ft
- Depth: 3 in
- Bag size: 2 ft³
- Waste / overage: 10 %
- • Keep mulch a few inches away from tree trunks and house walls.
Results are estimates for planning only. Supplier specifications, product yields, site conditions and local codes vary. Confirm quantities with your supplier or a qualified professional before you buy or build.
How this is calculated
Formulas
- Rectangle area = length × width. Circle area = π × (diameter ÷ 2)².
- Volume = area × depth.
- Total volume = volume × (1 + waste %).
- Bags = total volume ÷ bag size, rounded up.
Assumptions
- The bed is flat and mulched to a uniform depth.
- Bag sizes vary by brand. Enter the size printed on the bag you intend to buy (default 2 ft³ or 50 L).
- For irregular beds, split the area into rectangles and circles and add the results.
Worked examples: common projects
A round bed 3 m across, 8 cm deep
Circle, diameter 3 m, depth 8 cm, bag size 50 L.
Mulch needed, including waste
0.62 cubic metres
- Total volume (incl. 10% waste): 0.62 m³ (622 L)
- Bags (50 L each): 13
A 30 × 6 ft front-yard bed, 3 in deep
Rectangle, length 30 ft, width 6 ft, depth 3 in, bag size 2 ft³.
Mulch needed, including waste
1.83 cubic yards
- Total volume (incl. 10% waste): 1.83 yd³ (49.5 ft³)
- Bags (2 ft³ each): 25
A tree ring 4 ft across, 3 in deep
Circle, diameter 4 ft, depth 3 in, bag size 2 ft³.
Mulch needed, including waste
0.13 cubic yards
- Total volume (incl. 10% waste): 0.13 yd³ (3.5 ft³)
- Bags (2 ft³ each): 2
Quick reference
Mulch coverage by depth
Bags are 2 cubic feet. Round bag counts up.
| Depth | Area covered by 1 yd³ | Yards per 100 sq ft | 2 ft³ bags per 100 sq ft |
|---|---|---|---|
| 1 in | 324 sq ft | 0.31 | 5 |
| 2 in | 162 sq ft | 0.62 | 9 |
| 3 in | 108 sq ft | 0.93 | 13 |
| 4 in | 81 sq ft | 1.23 | 17 |
Cubic yards of mulch by area and depth
Volume only, before waste. A cubic yard is 13.5 bags of 2 cubic feet.
| Area | 2 in deep | 3 in deep | 4 in deep | 6 in deep |
|---|---|---|---|---|
| 100 sq ft | 0.62 yd³ | 0.93 yd³ | 1.23 yd³ | 1.85 yd³ |
| 250 sq ft | 1.54 yd³ | 2.31 yd³ | 3.09 yd³ | 4.63 yd³ |
| 500 sq ft | 3.09 yd³ | 4.63 yd³ | 6.17 yd³ | 9.26 yd³ |
| 1,000 sq ft | 6.17 yd³ | 9.26 yd³ | 12.35 yd³ | 18.52 yd³ |
| 2,000 sq ft | 12.35 yd³ | 18.52 yd³ | 24.69 yd³ | 37.04 yd³ |
Before you buy mulch
Depth drives the quantity more than anything else. A 3-inch layer needs 50% more mulch than a 2-inch layer. Thicker layers do not always help plants, so check guidance for what you are growing.
Bags are convenient for small beds. For larger areas, a bulk delivery measured in cubic yards or cubic metres is usually cheaper per unit. Edging a bed with stone? Estimate it with the gravel calculator or plan borders with the paver calculator.
Applying mulch well
Clear weeds, then spread mulch evenly to the depth you planned, and pull it back from tree trunks and the base of plants so the bark can breathe. A thick pile against a trunk holds moisture against it. Spread the first layer thinner than you think you need and add more if the soil still shows.
Mulch breaks down over time. Rather than piling on a new thick layer every year, check the depth and top it up to your target.
Mulch calculator in square feet or square metres
Choose Known area to enter square feet or square metres directly, for example when you have added up several beds. At 3 inches deep, 500 square feet needs 125 cubic feet, or 4.63 cubic yards. At 2 inches it needs 3.09 cubic yards.
Frequently asked questions
How much area does a cubic yard of mulch cover?
About 108 square feet at 3 inches deep, 162 square feet at 2 inches, or 324 square feet at 1 inch.
How many 2 cubic foot bags are in a cubic yard?
13.5, because a cubic yard is 27 cubic feet. In practice you buy 14 bags.
How deep should I spread mulch?
2–3 inches (5–8 cm) is a common recommendation for garden beds. Keep it a few inches clear of tree trunks and house walls.
Should I add extra for settling?
A small allowance, such as 5–10%, covers uneven ground and settling. The default here is 10%.
How many bags of mulch do I need for 100 square feet?
At 3 inches deep you need 25 cubic feet, which is 13 bags of 2 cubic feet. At 2 inches it is 17 cubic feet, or 9 bags.
When should I top up mulch?
When the layer has thinned below your target depth, typically once a year or so depending on the mulch. Measure the depth rather than adding a full new layer by default.
How much mulch do I need for 500 square feet?
At 3 inches deep, 500 square feet needs 125 cubic feet, which is 4.63 cubic yards or about 63 bags of 2 cubic feet. At 2 inches it needs 3.09 cubic yards.
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Results are estimates for planning only. Supplier specifications, product yields, site conditions and local codes vary. Confirm quantities with your supplier or a qualified professional before you buy or build.