How much compost do I need?
Multiply the area by the depth of compost you will spread: square feet × inches ÷ 324 gives cubic yards.
cubic yards = square feet × depth (in) ÷ 324
For 1,000 sq ft at 1 inch: 1,000 × 1 ÷ 324 = 3.09 cubic yards, the 3.1 cubic yards Penn State gives; 2 inches is 6.2 cubic yards.[1] Colorado State rounds the same rule to about 3 cubic yards (81 cubic feet) per inch per 1,000 sq ft.[3] The depth is what you spread on top before any tilling, not the depth you mix it into.
Compost per 1,000 sq ft by depth
Each quarter inch over 1,000 sq ft takes about 0.8 cubic yards.
| Depth | Cubic yards | Cubic feet | Typical use |
|---|---|---|---|
| ¼ in | 0.77 | 21 | Lawn top-dressing, one pass |
| ½ in | 1.54 | 42 | Two top-dressing passes |
| 1 in | 3.09 | 83 | Light amendment before seeding or sod |
| 2 in | 6.17 | 167 | New garden bed, tilled in |
| 3 in | 9.26 | 250 | Very poor soil or raised-bed top-up |
Cornell's sports-turf guide lists 0.8 cubic yards for ¼ inch and 1.5 for ½ inch per 1,000 sq ft.[2]
Compost for lawns, beds and new gardens
- Established lawns: top-dress no more than ¼ inch per application.[2] Penn State uses the same ¼ inch surface rate on existing turf.[1]
- Before seeding or sod: spread compost and work it into the top 4–6 inches.[1] Purdue's sod guide suggests 1–3 cubic yards per 1,000 sq ft mixed at least 6–8 inches deep.[4] The sod calculator and grass seed calculator size the rest of the job.
- Raised beds: Maryland Extension targets 25–50% organic matter by volume in raised-bed soil; the raised bed soil calculator splits a bed into compost and topsoil.[5]
Mixing with soilIf you are buying a blend of soil and compost, size the whole volume with the soil calculator instead.
How much does a yard of compost weigh?
A cubic yard of screened compost at about 50% moisture weighs around 1,000 lb, and very wet compost can exceed 1,500 lb.[6]
The calculator uses 0.4–0.8 US tons per cubic yard (about 801–1,601 lb), the typical range. Ask the supplier whether a price is per yard or per ton before comparing quotes, and use the tons to yards calculator to convert.
Common compost mistakes
- Top-dressing too thick: more than ¼ inch at once can smother turf.[2]
- Confusing spread depth and tilling depth: 2 inches spread and tilled 6 inches deep is still 6.2 cubic yards per 1,000 sq ft.[1]
- Buying by the bag for big areas: 3.1 cubic yards is 84 bags of 1 cu ft; bulk delivery is usually simpler past a cubic yard or two.
Frequently asked questions
How much compost do I need per 1,000 square feet?
How deep should compost be tilled in?
Work it into the top 4–6 inches before planting a lawn or bed.[1]
How much does a yard of compost weigh?
Around 1,000 lb at 50% moisture; very wet compost can be over 1,500 lb.[6]
How thick should I top-dress a lawn with compost?
No more than ¼ inch per application.[2]