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Cubic yards, cubic feet and bags of compost for lawn topdressing, new lawns and garden beds at extension-recommended depths.
With these inputs:
| Result | Value |
|---|---|
| Compost to order | 1.85 yd³ |
| Cubic feet | 50 cu ft |
| 1 cu ft bags | 50 bags |
| 1.5 cu ft bags | 34 bags |
| Area | 200 sq ft |
| Depth | 3 in (guide 3–4 in) |
| Per 1,000 sq ft at this depth | 9.26 yd³ |
Depths from Oregon State University Extension (EM 9308): lawn topdressing 1/4–1/2 in, new lawns 1–2 in, existing beds 1/4–1 in a year, new beds 3–4 in worked into the top 8–12 in. Bulk compost is sold by the cubic yard (27 cu ft); bagged compost by the cubic foot.
How much compost you need depends on the job: a quarter inch over a lawn, an inch or two for a new lawn, three or four inches worked into a new bed. Pick the job (or enter your own depth) and the area for the cubic yards to order in bulk and the number of 1 or 1.5 cu ft bags.
Area × depth in feet ÷ 27 gives cubic yards. A 20 × 10 ft new bed with 3 in of compost needs 1.85 yd³ (50 cu ft, or 50 one-cubic-foot bags). Topdressing 1,000 sq ft of lawn 1/4 in deep takes 0.77 yd³.
Oregon State University Extension recommends topdressing 1/4 to 1/2 in deep — about 0.77 to 1.54 cubic yards per 1,000 sq ft — ideally after core aeration so it reaches the root zone. For a new lawn, work 1 to 2 in into the soil before seeding or laying sod.
For a new bed, spread 3 to 4 in and work it into the top 8 to 12 in of soil (OSU Extension). For an existing bed, add 1/4 to 1 in a year on the surface. Oregon State's own check: 7.5 cubic yards covers 800 sq ft about 3 in deep.
A cubic yard is 27 cubic feet, so 27 one-cubic-foot bags or 18 bags of 1.5 cu ft. Beyond about 2 yards, bulk delivery is usually cheaper than bags.
No. Compost is decomposed organic matter used to improve soil; topsoil is mineral soil that holds plants up. Beds and lawns are usually built with topsoil and improved with a few inches of compost — the topsoil calculator sizes the soil.
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