Compost Calculator
Calculate cubic yards and bags of compost to top-dress lawns or amend beds.
Loading calculator…
Currency: Amounts are calculated in the currency you select; this site does not convert between currencies and does not use live exchange rates.
What this tool does
The Compost Calculator works out how much compost you need to spread over a garden bed or lawn at a chosen depth — from a thin ¼-inch top-dressing to a 3-inch bed amendment — in yards and bags.
How to use the Compost Calculator
- Measure the bed length and width.
- Enter the compost depth you want.
- Choose the bag size you plan to buy.
- Enter the bulk price per cubic yard to compare.
- Buy the bags shown or order the bulk yards.
Formula
cu ft = L × W × (D ÷ 12); yd³ = cu ft ÷ 27; bags = ⌈cu ft ÷ bag size⌉
- L, W
- Length and width (ft)
- D
- Depth (in)
- bag size
- Bag volume in cu ft
Worked example
A 20 × 10 ft bed at 2 in deep using 1.5 cu ft bags.
Inputs
- Length20 ft
- Width10 ft
- Depth2 in
- Bag size1.5 cu ft
- Price per cubic yard (bulk)$45
Result
- Compost needed1.23 cu yd
- Bags (1.5 cu ft)23
- Volume33.33 cu ft
- Bulk cost estimate$55.56
Compost coverage by depth
| Depth | Coverage of 1 cu yd | Coverage of a 2 cu ft bag |
|---|---|---|
| 1 in | 324 sq ft | 24.0 sq ft |
| 2 in | 162 sq ft | 12.0 sq ft |
| 3 in | 108 sq ft | 8.0 sq ft |
| 4 in | 81 sq ft | 6.0 sq ft |
| 6 in | 54 sq ft | 4.0 sq ft |
Results explained
- Compost needed
- Cubic yards for a bulk delivery.
- Bags
- Bags to buy, rounded up to whole bags.
- Volume
- Total cubic feet.
- Bulk cost
- Yards × price per yard, excluding delivery.
Frequently asked questions
Mix 2–3 inches into the top 6–8 inches of soil when preparing new beds.
¼ to ½ inch, raked in after aeration.
About 162 sq ft at 2 in deep or 1,296 sq ft at ¼ in.
Roughly 800–1,200 lb depending on moisture.
Yes; beds that are more than about 30% compost can hold excess nutrients and stay too wet.