Landscaping calculator
Compost calculator
Work out how much compost the job takes, whether you are topdressing a lawn at a quarter inch or amending a bed to a full two inches.
Your project
Lawn topdressing is 0.25-0.5". Bed amendment is 1-3" tilled into the top 6".
Crews typically order 5-10% extra to cover compaction, spillage and uneven subgrade.
Compost needed
0.78
cubic yards · includes 5% waste
- Area
- 480 sq ft
- Volume (cubic feet)
- 21 cu ft
- 1 cu ft bags
- 21 bags
- Approximate weight
- 945 lb
- Weight in tons
- 0.47 tons
- Estimated cost
- $35
- Coverage of one cubic yard
- 648 sq ft at this depth
Topdressing works best applied thin and repeated. A quarter inch twice a year builds soil faster than an inch once, and it does not smother the turf.
The shareable link reopens this calculator with your exact inputs.
How much compost do I need?
The maths is the same as mulch — area times depth divided by 27 — but the depths are far smaller, which is exactly why people over-order. Topdressing 1,000 sq ft of lawn at a quarter inch takes 20.8 cubic feet: under a cubic yard.
For bed amendment, the rule of thumb is one to three inches spread on the surface and tilled into the top six inches of soil. That puts the finished bed at roughly 20-30% organic matter by volume, which is where most vegetables want it.
Compost weighs about 45 lb per cubic foot damp, or 1,200 lb per cubic yard — noticeably lighter than topsoil and much heavier than bark mulch. A wheelbarrow holds around 3 cubic feet, so a yard is nine barrow loads.
Topdressing a lawn with compost
Aerate first if the soil is compacted, then spread compost a quarter to half an inch deep and drag it in with the back of a rake or a levelling lute. The grass blades should still be visible when you finish — if the lawn looks brown, the layer is too thick.
Screened fine compost is worth the premium here. Coarse compost sits on top, does not work into the aeration holes, and takes a full season to disappear.
Spring or early autumn, while the grass is actively growing, gives the best result. Topdressing dormant turf just leaves a layer sitting there through the season.
Compost coverage per cubic yard
How far one cubic yard goes at typical application depths.
| Depth | Sq ft per cu yd | Cu yd per 1,000 sq ft | Job |
|---|---|---|---|
| 0.25" | 1,296 | 0.77 | Lawn topdressing, light |
| 0.5" | 648 | 1.54 | Lawn topdressing, standard |
| 1" | 324 | 3.09 | Light bed amendment |
| 2" | 162 | 6.17 | Bed amendment or compost mulch |
| 3" | 108 | 9.26 | New bed, heavy amendment |
Frequently asked questions
+How much compost do I need per square foot?
At one inch deep, 0.083 cubic feet per square foot — so 100 sq ft takes 8.3 cubic feet. Divide the depth in inches by 12 and multiply by the area to get cubic feet directly.
+How much does a cubic yard of compost weigh?
Roughly 1,000-1,400 lb depending on moisture, so about half to two thirds of a US ton. Fresh, wet compost sits at the top of that range.
+How much compost to topdress 1,000 square feet?
About 0.8 cubic yards at a quarter inch, or 1.5 cubic yards at half an inch. Half an inch is the most you want in one application on established turf.
+How many bags of compost make a cubic yard?
Twenty-seven bags at 1 cubic foot, or 18 at the 1.5 cubic foot size. Bulk compost is typically a third of the bagged cost per yard.
+Can you use too much compost?
Yes. Beyond about 30% organic matter by volume, soils hold excess phosphorus and salts, and heavy repeated applications can push phosphorus into runoff. Thin, regular applications beat one thick dose.
+Compost or mulch — which goes on top?
Compost first, worked into or laid on the soil, then mulch over it. Compost feeds the soil and breaks down fast; mulch is the protective layer that keeps moisture in and weeds down.