How Much Compost Do I Need? Lawn Top Dressing, Raised Beds and Per 100 Sq Ft

The garden center sells compost in 2 cu ft bags, the landscape yard sells it by the cubic yard, and your lawn is 5,000 sq ft. Spread 1/4 inch over 1,000 sq ft of lawn and you need 20.8 cubic feet, about 0.77 cubic yards or 11 bags of 2 cu ft. The University of Maryland Extension says about ¼ to ¾ inch of topsoil or compost can usually go on turf without smothering the crown. For a 4 × 8 raised bed, Maryland Extension says to add 2 to 4 inches of compost and mix it into the top 4 inches of soil: 5.3 to 10.7 cubic feet.

Free calculator: enter your area and depth in our free mulch and soil calculator for cubic feet, yards and bags. No sign-up.

How much compost to top-dress a lawn

Cubic feet; cubic yards; bags of 2 cu ft (rounded up).

100 sq ft, 1/4 in — 2.1 cu ft; 0.08 yd; 2 bags

100 sq ft, 1/2 in — 4.2 cu ft; 0.15 yd; 3 bags

500 sq ft, 1/4 in — 10.4 cu ft; 0.39 yd; 6 bags

500 sq ft, 1/2 in — 20.8 cu ft; 0.77 yd; 11 bags

1,000 sq ft, 1/4 in — 20.8 cu ft; 0.77 yd; 11 bags

1,000 sq ft, 1/2 in — 41.7 cu ft; 1.54 yd; 21 bags

2,500 sq ft, 1/4 in — 52.1 cu ft; 1.93 yd; 27 bags

5,000 sq ft, 1/4 in — 104.2 cu ft; 3.86 yd; 53 bags

5,000 sq ft, 1/2 in — 208.3 cu ft; 7.72 yd; 105 bags

Per 100 sq ft, each full inch of compost is 8.3 cu ft, about 0.31 cubic yards. Past 2 or 3 yards, compare bulk with bags. See how many bags in a yard.

Not a fit: more than ¾ inch at once over living grass. In Maryland, the Extension notes that state law ties top-dressing amounts to a soil test and a compost nutrient analysis.

How much compost for a raised bed

Adding compost to a bed that already has soil (2 to 4 in of compost mixed into the top 4 in, per Maryland Extension):

4 × 4 ft bed — 2.7 to 5.3 cu ft; 2 to 3 bags

3 × 6 ft bed — 3.0 to 6.0 cu ft; 2 to 3 bags

4 × 8 ft bed — 5.3 to 10.7 cu ft; 3 to 6 bags

4 × 12 ft bed — 8.0 to 16.0 cu ft; 4 to 8 bags

Filling a new bed 12 inches deep, Maryland Extension suggests compost and topsoil in a 1:2 or 1:1 ratio, so compost is one-third to one-half of the fill:

4 × 8 ft bed, 12 in — 32 cu ft total; 10.7 to 16 cu ft of compost; 6 to 8 bags

For other sizes and depths, use the raised bed calculator or see how deep a raised bed should be.

How to measure for compost

Lawn area: length × width of each grass section, in feet.

Depth in feet: inches ÷ 12. 1/4 in is 0.0208 ft; 1/2 in is 0.0417 ft.

Cubic feet: square feet × depth in feet. 1,000 × 0.0208 = 20.8.

Cubic yards: cubic feet ÷ 27. Bags: cubic feet ÷ bag size, rounded up.

Bagged soil check: Maryland Extension notes that bags labeled "organic soil" typically don't actually contain topsoil, so read the bag before you count it as either.

Tools to move and spread compost (#ad)

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Gorilla Carts 4 Cu Ft Poly Dump Cart — a 4 cu ft poly tub rated for 600 lb, with a quick-release dump, per the maker. A cubic yard is 27 cu ft, so about 7 cart loads from the driveway pile to the lawn. See it on Amazon

Landzie 24 in Compost and Peat Moss Spreader — a 24-inch steel mesh drum you push across the lawn, made to break up clumps as it rolls, per the maker. For spreading a thin, even 1/4 inch layer. See it on Amazon

Leveling low spots? See how much topsoil to level a lawn.

Compost amount FAQ

How much compost do I need for 1,000 square feet? 20.8 cu ft (0.77 yd) at 1/4 inch, or 41.7 cu ft (1.54 yd) at 1/2 inch.

How much compost to top-dress a lawn? Maryland Extension says about ¼ to ¾ inch can usually go on turf without smothering the crown. At 1/4 inch, plan on 0.77 yd per 1,000 sq ft.

How many bags of compost for a 4 × 8 raised bed? To top up with 2 to 4 inches, 3 to 6 bags of 2 cu ft. To fill a new 12-inch bed, 6 to 8 bags of compost plus topsoil.

How much compost per 100 square feet? 2.1 cu ft at 1/4 inch, 4.2 cu ft at 1/2 inch, 8.3 cu ft at 1 inch.

How much compost to mix into a raised bed? Maryland Extension says to add 2 to 4 inches and mix it with the top 4 inches of soil.

Free calculator: get yards and bags for any lawn or bed in the free mulch and soil calculator.

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Sources: University of Maryland Extension, Improving a Struggling Lawn and Repairing Damage; University of Maryland Extension, Soil to Fill Raised Beds.