Enter the size of the bed and how deep you want the mulch to see how many cubic yards or bags to buy.
How mulch is calculated
Mulch is sold by volume, so multiply the area of the bed by the depth. The depth is in inches, so divide it by 12 to get feet first.
Cubic feet = area (sq ft) × depth (in) ÷ 12
Cubic yards = cubic feet ÷ 27
Bags = cubic feet ÷ bag size, rounded up
For a round bed, the area is π × radius², where the radius is half the diameter.
Worked example
A 10 × 10 ft bed is 100 sq ft. At 3 inches deep: 100 × 3 ÷ 12 = 25 cubic feet. Divide by 27 to get 0.926 cubic yards. In bags, that's 25 ÷ 2 = 12.5, so 13 bags of 2 cu ft, or 25 ÷ 3 = 8.3, so 9 bags of 3 cu ft.
How deep should mulch be?
University of Illinois Extension recommends a 2 to 4 inch layer on well-drained soil: about 2 to 3 inches of fine or composted mulch, and 3 to 4 inches of coarse mulch like bark chunks. Keep mulch at least 4 inches away from tree trunks, and don't pile it up against stems (so-called "volcano mulching").
| Depth | Area one cubic yard covers | Area a 2 cu ft bag covers |
|---|
| 2 in | 162 sq ft | 12 sq ft |
| 3 in | 108 sq ft | 8 sq ft |
| 4 in | 81 sq ft | 6 sq ft |
Limitations
- Topping up: if there's old mulch, measure what's left and only add the difference.
- Settling: fresh, fluffy mulch settles. Some gardeners add a little extra.
- Odd shapes: split the bed into rectangles and circles, add the areas, and use the "Square feet" option.
- Bag sizes vary: check the bag. Most are 2 or 3 cu ft, but some are 1.5 cu ft.
Sources
How we checked this
Before every update, this calculator is run in a real browser with these known answers, and it must match all of them:
- 10 × 10 ft bed, 3 in deep: 25 cu ft = 0.926 cubic yards ✓
- Same bed: 13 bags of 2 cu ft or 9 bags of 3 cu ft ✓
- Round bed 10 ft across, 3 in deep: 0.727 cubic yards ✓
- 1,000 sq ft at 2 in: 6.17 cubic yards, 84 bags of 2 cu ft ✓
- Depth 0 shows no answer ✓
- Pricing 3 cu ft bags: the sentence counts 9 bags of 3 cu ft ✓
- Half a square foot at 1 inch: 1 inch, 1 bag (singular) ✓
Last checked October 26, 2026. Spotted something wrong? The math is done in your browser with the formula shown on this page, so you can check any result by hand.
Questions people ask
How many bags of mulch are in a yard?
A cubic yard is 27 cubic feet, so it's 13.5 bags of 2 cu ft or 9 bags of 3 cu ft.
How much area does a yard of mulch cover?
At 3 inches deep, one cubic yard covers 108 sq ft. At 2 inches it covers 162 sq ft, and at 4 inches 81 sq ft.
How much mulch do I need for a 10 × 10 bed?
At 3 inches deep, 25 cubic feet: about 0.93 cubic yards, 13 bags of 2 cu ft or 9 bags of 3 cu ft.
Is it cheaper to buy mulch in bags or bulk?
For more than a cubic yard or two, bulk mulch is usually cheaper per cubic foot, but it often has a delivery fee. Compare the price per cubic foot: divide the bag price by its size.
How deep should mulch be around trees?
2 to 4 inches, kept at least 4 inches away from the trunk. Mulch piled against the bark can trap moisture and cause rot.