How much mulch do I need?
Multiply the bed length × width × depth in inches and divide by 12 for cubic feet, then by 27 for cubic yards. A 20 × 10 ft bed 3 in deep holds 50 cu ft, which is 1.85 cubic yards, or 25 bags of 2 cu ft.
Worked example: a 20 × 10 ft bed
- Bed area: 20 × 10 = 200 sq ft.
- Convert depth to feet: 3 in ÷ 12 = 0.25 ft.
- Volume: 200 × 0.25 = 50 cu ft.
- Cubic yards: 50 ÷ 27 = 1.85 cu yd.
- Bags: 50 ÷ 2 = 25 bags of 2 cu ft.
How much area does mulch cover?
Coverage depends only on depth. One cubic yard holds 27 cu ft, which spreads to 324 sq ft at 1 inch; divide by the depth for any other thickness.
| Depth | One cubic yard | One 2 cu ft bag | One 3 cu ft bag |
|---|---|---|---|
| 1 in | 324 sq ft | 24 sq ft | 36 sq ft |
| 2 in | 162 sq ft | 12 sq ft | 18 sq ft |
| 3 in | 108 sq ft | 8 sq ft | 12 sq ft |
| 4 in | 81 sq ft | 6 sq ft | 9 sq ft |
Mulch needed by bed size
Cubic yards at 2 and 3 inches deep, and 2 cu ft bags at 3 inches.
| Bed | Area | At 2 in | At 3 in | Bags at 3 in |
|---|---|---|---|---|
| 4 × 8 ft | 32 sq ft | 0.20 cu yd | 0.30 cu yd | 4 |
| 10 × 5 ft | 50 sq ft | 0.31 cu yd | 0.46 cu yd | 7 |
| 20 × 4 ft | 80 sq ft | 0.49 cu yd | 0.74 cu yd | 10 |
| 20 × 10 ft | 200 sq ft | 1.23 cu yd | 1.85 cu yd | 25 |
| 30 × 10 ft | 300 sq ft | 1.85 cu yd | 2.78 cu yd | 38 |
| 50 × 10 ft | 500 sq ft | 3.09 cu yd | 4.63 cu yd | 63 |
How the calculator works
Volume (cu ft) = length × width × depth (in) ÷ 12
Cubic yards = volume ÷ 27
Bags = volume ÷ bag size, rounded up
For an irregular bed, split it into rectangles and add them up, or use the square footage calculator first. For a round tree ring, the area is 3.14 × radius × radius.
Frequently asked questions
How many bags of mulch are in a cubic yard?
A cubic yard is 27 cu ft: 13.5 bags of 2 cu ft, 9 bags of 3 cu ft or 18 bags of 1.5 cu ft.
How much does a 2 cu ft bag of mulch cover?
About 12 sq ft at 2 inches deep, 8 sq ft at 3 inches and 6 sq ft at 4 inches.
How deep should mulch be?
Most beds do well with 2 to 3 inches. Top up an existing bed with 1 to 2 inches, and avoid going much deeper than 4 inches or piling mulch against trunks.
Should I buy mulch in bags or in bulk?
Bags suit small beds and top-ups. Past two or three cubic yards, bulk delivery from a landscape supplier is usually cheaper and quicker to spread.
Can I use this for topsoil or compost?
Yes. The volume math is the same; enter the bag size shown on the topsoil or compost bag.