Mulch Calculator
Enter the bed size and depth to get cubic yards, cubic feet and the number of bags.
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Multiply the bed’s length by its width to get square feet, then multiply by the depth in feet (inches divided by 12). That gives cubic feet. Divide by 27 for cubic yards, which is how bulk mulch is sold. One cubic yard covers about 108 square feet at 3 inches deep, or about 162 square feet at 2 inches.
Bagged or bulk?
Bagged mulch is usually 2 or 3 cubic feet per bag. A cubic yard is 27 cubic feet, so it takes 13 to 14 two-cubic-foot bags to equal one yard. For more than about 2 cubic yards, bulk delivery from a landscape supplier is usually cheaper, but check the delivery fee and where the pile can go.
How deep should mulch be?
Two to 3 inches suits most flower beds and shrubs. Keep mulch a few inches away from tree trunks and stems, and avoid piling it into a volcano shape, which traps moisture against the bark. When refreshing an existing bed, you usually only need to top up to 2 inches total.
Irregular beds
For a curved bed, break the shape into rectangles and circles, calculate each, and add the cubic yards together. Use the extra percentage to cover uneven ground and settling.
Worked examples
- Three flower beds: each 10 ft × 4 ft, mulched 3 inches deep. Each bed needs 40 × 0.25 = 10 cubic feet, so the three need 30 cubic feet, or about 1.1 cubic yards. With 10% extra, plan on about 33 cubic feet. That is 17 bags of 2 cubic feet or 11 bags of 3 cubic feet.
- Tree ring: a circle 6 ft across (3 ft radius) at 3 inches deep. The area is 3.14 × 3 × 3 = 28.3 square feet, and the volume is 28.3 × 0.25 = 7.1 cubic feet. Take off a little for the trunk and any bare space you leave around it.
Coverage by depth
| Depth | Area covered by 1 cubic yard |
|---|---|
| 2 inches | 162 sq ft |
| 3 inches | 108 sq ft |
| 4 inches | 81 sq ft |
Choosing a mulch
- Shredded hardwood knits together, stays in place on slopes, and breaks down gradually into the soil.
- Bark nuggets look chunky and last longer, but they can wash or blow away.
- Pine straw is common in the southeastern US and is usually sold by the bale, not the cubic yard, so this calculator’s volume will not translate directly. Ask the seller for bale coverage.
- Compost feeds the soil but breaks down quickly, so it is often used under a layer of coarser mulch.
Common mistakes
- Piling it too deep. More than 3 to 4 inches can keep water and air from reaching roots.
- Covering the trunk or stems. Leave a small gap so the bark can dry out.
- Ignoring what is already there. If the old layer is still 1 inch deep, you only need to add enough to reach the depth you want.
Frequently asked questions
How many bags make a cubic yard?
About 13.5 bags of 2 cubic feet, or 9 bags of 3 cubic feet.
How often should I replace mulch?
Organic mulch breaks down over time. Most gardeners top it up every year or two, rather than removing the old layer.