Do the math
How much mulch do you need?
The Simple Answer
A cubic yard of mulch covers about 108 square feet at a depth of 3 inches. Measure the area, divide by the coverage for the depth you want, and round up.
Mulch is sold by the cubic yard in bulk and by the cubic foot in bags. The sum is the same either way, and it is short once you know how much a cubic yard covers.
Why 108
A cubic yard is a cube 3 feet on each side, so it holds 3 × 3 × 3 = 27 cubic feet. Spread over a surface, that volume covers more area the thinner you make the layer. At 3 inches, which is a quarter of a foot, it covers 27 ÷ 0.25 = 108 square feet.
| Depth | Coverage |
|---|---|
| 2 inches | 162 square feet |
| 3 inches | 108 square feet |
| 4 inches | 81 square feet |
A bed that is 10 feet by 12 feet, 3 inches deep
Area: 10 × 12 = 120 square feet
Mulch: 120 ÷ 108 = 1.11 cubic yards
That is about 30 cubic feet. In bags of 2 cubic feet, 30 ÷ 2 = 15 bags.
| Area | 2 inches | 3 inches | 4 inches |
|---|---|---|---|
| 50 square feet | 0.31 | 0.46 | 0.62 |
| 100 square feet | 0.62 | 0.93 | 1.23 |
| 200 square feet | 1.23 | 1.85 | 2.47 |
Things people often miss
- Round up. It is easier to have a little left over than to make a second trip.
- Curved beds: measure the longest and widest points and take a bit less than the full rectangle, or split the bed into rectangles and add them up.
- Old mulch counts. If there is already a layer, you only need to add enough to reach the depth you want.
- Bag sizes vary. Check the number of cubic feet on the label before you divide.
Mulch Calculator: Enter the length, width and depth of the bed to see the cubic yards and the number of bags.