Free compost calculator — yards, bags and weight for any area
Enter the area and the depth you are spreading and get cubic yards, how many bags that is, and roughly what it weighs. Add several shapes for a yard with beds and lawn. No signup, no email.
How deep to spread compost
The depth decides everything, and compost is spread thinner than mulch or topsoil:
- Topdressing an established lawn — ¼" to ½". Any deeper smothers the grass. Rake it in and water.
- New lawn or seeding — 1" to 2" tilled into the top 6" of soil before you seed or lay sod.
- Vegetable and flower beds — 2" to 3" worked into the soil at the start of the season, then 1" a year after that.
- Around trees and shrubs — 1" to 2" out to the drip line, kept off the trunk.
- Filling raised beds — compost is usually a third of the mix, with topsoil and something coarse making up the rest; enter the full bed depth and take a third.
How the math works
- Cubic yards = area (sq ft) × depth (ft) ÷ 27. One cubic yard covers 324 sq ft at 1", or 648 sq ft at ½".
- Weight is figured at about 0.45 tons per cubic yard for finished compost, which varies a lot with moisture — wet compost can run 30% heavier.
- Bags at 1 cu ft each, rounded up once at the end, not per bed.
- Under a cubic yard, buy bagged. Bulk delivery carries a minimum order and a delivery fee that swamps the material cost at that size.
Worked example
Topdressing a 5,000 sq ft lawn at ½" needs 5,000 × (0.5 ÷ 12) ÷ 27 = 7.7 cubic yards, about 3.5 tons. Three 4 × 8 raised beds filled 12" deep are 32 cu ft, so a third compost is a little under 11 cu ft — 11 bags.
Turn it into a quote
Landscapers: Copy list puts the yardage on your clipboard. Price the spreading with the landscaping pricing calculator and send it with the landscaping estimate template. For the rest of the yard, see the mulch, topsoil and sod calculators.
FAQ
How much compost do I need for a 1,000 sq ft lawn?
At a ½-inch topdressing, about 1.5 cubic yards. At ¼-inch, which is enough for a healthy lawn, about 0.8 yards — roughly 21 bags.
How many bags of compost in a cubic yard?
27 one-cubic-foot bags, or about 18 of the 1.5 cu ft bags. Over about 15 bags, bulk delivery is usually cheaper if you can take a minimum load.
How much does a yard of compost weigh?
Roughly 900 lb, or 0.45 tons, for finished screened compost at normal moisture. Wet compost can top 1,200 lb. A half-ton pickup carries about one yard safely.
How thick should I spread compost on a lawn?
No more than ½-inch on an established lawn, and ¼-inch is plenty for annual feeding. Thicker layers block light and air from the grass. Spread, rake in, then water.
Can I use compost instead of topsoil?
Not on its own for filling or grading. Compost breaks down and settles, and pure compost holds too much water for roots. Use it as a third of a raised-bed mix, or till 1–2-inch into existing soil.
Is this calculator free?
Yes, completely. No account, no email, no download. It runs in your browser and we never see your numbers.