Bulk compost is usually ordered by the cubic yard, and the calculator reports cubic yards and cubic feet so you can check either way. A cubic yard is 27 cubic feet. The layer depth sets the answer, and each use has its own depth, as the sections below show.
How to use this calculator
- Choose the shape of the area. Rectangle covers lawns, beds and slopes, circle suits a round bed, and ring fits the ground around a tree.
- Enter the length and width in feet. For a lawn, measure only the grass you will top dress, not the whole yard.
- Choose the layer depth for your use. The section on depth lists the figure for lawns, beds, trees and shrubs, and erosion control.
- For a tree ring, enter the outside diameter and the inside diameter. The inside measure is the open center around the trunk, which the compost should not cover.
- Order the cubic yards shown, and add a little for uneven ground. The calculator gives the exact volume at the depth you enter.
Worked examples
Lawn top dressing
40 ft × 25 ft, 0.25 in deep
- cubic yards
- 0.772
- cubic feet
- 20.83
Perennial bed
12 ft × 6 ft, 2 in deep
- cubic yards
- 0.444
- cubic feet
- 12
Tree ring
ring 10 ft outside / 2 ft inside, 3 in deep
- cubic yards
- 0.698
- cubic feet
- 18.85
Slope against erosion
30 ft × 4 ft, 4 in deep
- cubic yards
- 1.48
- cubic feet
- 40
Cubic yards of compost for common lawn and bed sizes
| Area | 0.25 in deep | 2 in deep | 4 in deep |
|---|---|---|---|
| 10 × 10 ft | 0.077 | 0.617 | 1.23 |
| 20 × 20 ft | 0.309 | 2.47 | 4.94 |
| 40 × 25 ft | 0.772 | 6.17 | 12.35 |
| 30 × 4 ft | 0.093 | 0.741 | 1.48 |
Cubic yards, exact volume without extra for waste.
Picking the layer depth by use
- Lawn top dressing: 0.25 inch. A cubic yard covers 1,296 square feet at this depth.
- Garden beds, annuals and perennials: 1 to 2 inches. At the top of that range, a cubic yard covers 162 square feet.
- Trees and shrubs: 1 to 3 inches, spread out from the trunk. At the top of that range, a cubic yard covers 108 square feet.
- Erosion control: 2 to 4 inches on bare or sloping ground. At the top of that range, a cubic yard covers 81 square feet.
Adding to an existing layer
Compost breaks down as soil life works it in and plants take it up, so a layer you spread one season is usually thinner by the next. Add more when the layer has worn thin, not on a fixed schedule.
Measure what is already there before you add more. A bed that still holds an earlier layer needs only the difference, so enter the depth you are adding rather than the depth you want in total.
What this estimate leaves out
The calculator works from volume only. It does not estimate weight, moisture or how much the layer will settle, and the depth ranges are guides rather than rules for your soil.
For slopes where water runs off, drainage problems or large erosion repairs, check local guidance or talk to a landscape professional before you spread material.
Common questions
How do I work out how much compost I need?
Multiply the length and width of the area, in feet, by the layer depth in feet to get cubic feet. Divide the result by 27 to get cubic yards. The calculator does both steps, so you only enter the area and the depth for your use.
How deep should compost be on a lawn?
A lawn top dressing is 0.25 inch, a thin layer that you work into the grass. Keep it thin enough that the blades still show, and do not bury the grass under a thick layer.
How often can I add compost to a lawn or bed?
There is no single schedule that suits every lawn and bed. Check the layer first: when it has worn thin, measure what is left, and enter only the depth you are adding so the total stays at the depth you want. For plant-specific advice, ask your local extension office.
How much compost goes around a tree?
Spread compost 1 to 3 inches deep, starting out from the trunk and leaving the center clear. Enter the outside and inside diameter of the ring, and the calculator shows the cubic yards for that ring. A mulch ring can go over the compost once it is in place, as long as it stays off the trunk.
How many cubic meters or liters is a cubic yard of compost?
A cubic yard is 0.765 cubic meter. A cubic foot is 28.317 liters, which helps if a bag is labeled in liters. Divide your total liters by the bag size to count bags.
How many bags of compost do I need?
Bags are usually 1 to 2 cubic feet, so start with the cubic feet shown by the calculator. A cubic yard is 27 cubic feet. Divide your cubic feet by the size printed on the bag, then round up to a whole bag. For a 2 cubic feet bag, divide by that size and round up.
How much does a cubic yard of compost weigh?
Finished, screened compost usually weighs about 1,000 lb per cubic yard per cubic yard, and very wet compost can top 1,500 lb per cubic yard. Moisture changes the weight a lot, so ask your supplier for the real number. Suppliers often sell by weight, and a short ton is 2,000 lb.