How deep to spread compost
Choose what you’re doing and the calculator fills in a starting depth from Oregon State Extension’s guidance. You can change it.
| Use | Oregon State guidance | Starting depth |
|---|---|---|
| New vegetable or flower bed | 3 to 4 inches, mixed into the top 8 to 12 inches | 3 in |
| Existing vegetable bed | ¼ to 1 inch a year, worked in | 1 in |
| Landscape bed | 3 to 4 inches, mixed 6 to 8 inches deep | 3 in |
| New lawn | 1 to 2 inches worked into the soil before seeding | choose 1 in |
| Existing lawn (topdressing) | ¼ to ½ inch after core aerating | ¼ in |
Enter the depth you spread on top, before mixing it in.
Working out the amount
Area × depth (in feet) = cubic feet. Divide by 27 for cubic yards, or by the bag size for bags.
- A 10 × 5 foot bed with 3 inches of compost needs 12.5 cubic feet: 7 bags of 2 cubic feet, or about 0.46 cubic yards.
- Topdressing a 1,000 square foot lawn ¼ inch deep needs about 20.8 cubic feet: 11 bags of 2 cubic feet, or about 0.77 cubic yards.
Oregon State’s rule of thumb: a 1 cubic foot bag covers 12 square feet at 1 inch deep, or 4 square feet at 3 inches. One cubic yard covers about 324 square feet at 1 inch and 108 square feet at 3 inches.
Bags or bulk
Bagged compost is labelled in cubic feet or litres. For whole-garden jobs, bulk compost by the cubic yard or cubic meter is usually more practical; suppliers set their own increments and minimum orders. To fill raised beds, use the raised bed soil calculator instead: Oregon State advises against filling beds with compost alone.
Keep your plan
Print your current plan or choose Save as PDF in the browser’s print dialog. Your inputs stay in a device draft when browser storage is available. An optional free account lets you save and sync the project in My projects. Calculating and printing stay open to everyone.