Compost Calculator
Cubic yards & bags of compost for beds and lawns
Amending soil or topdressing a lawn with compost? Enter the area and depth to get the cubic yards and bags you need.
How much compost to add?
Topdress an existing lawn with ¼–½ inch; amend a new bed with 2–3 inches worked into the top 6–8 inches of soil. The math is area × depth, converted here to both bags and cubic yards.
Compost: bags vs. bulk
Standard bags hold about 1.5 ft³, so roughly 18 bags equal a cubic yard. For a single raised bed, bags are convenient; for amending a whole garden or topdressing a lawn, bulk compost is far cheaper.
Why topdress with compost
A thin annual layer of compost feeds soil life, loosens clay, helps sandy soil hold water, and releases nutrients slowly without the burn risk of synthetic fertilizer. Rake lawn topdressing in so it settles to the soil surface rather than matting on the grass blades.
Compost Calculator: frequently asked questions
How thick should compost be on a garden bed?
2–3 inches worked into the top layer for a new bed; ¼–½ inch to topdress an established lawn.
How many bags of compost in a cubic yard?
About 18 standard 1.5-cubic-foot bags (27 ÷ 1.5).
Can you use too much compost?
Yes. More than a few inches can over-supply nutrients (especially phosphorus) and hold too much water. For most beds 1–3 inches worked in is plenty; topdress lawns with no more than ½ inch at a time.