Compost Calculator
Multiply length × width × depth in feet and divide by 27 for cubic yards. A new 10 × 10 ft garden bed with 3 inches of compost takes 0.93 cubic yards, or 25 bags of 1 cubic foot.
Updated October 19, 2026 · How we calculate
Worked example
A new 10 × 10 ft garden bed, 3 inches of compost:
- Area: 10 × 10 = 100 square feet
- Depth in feet: 3 ÷ 12 = 0.25 ft
- Volume: 100 × 0.25 = 25 cubic feet
- Cubic yards: 25 ÷ 27 = 0.926 cu yd
- Weight: 0.926 × 800 to 1,600 lb ÷ 2,000 = 0.37 to 0.74 tons
- Bags: 25 ÷ 1 = 25 1 cu ft bags
- Bags: 25 ÷ 2 = 13 2 cu ft bags
Source: Oregon State University Extension, EM 9217 Interpreting Compost Analyses (2018); University of Minnesota Extension, Interpreting your compost report
How to choose and how deep
How deep for each job
| Use | Depth | Source |
|---|---|---|
| Topdressing a lawn | ¼ to ½ inch, after core aeration | Oregon State University Extension, EM 9308 How to Use Compost (2021) |
| Before seeding or laying sod | 1 to 2 inches, tilled in | Oregon State University Extension, EM 9308 How to Use Compost (2021) |
| New garden bed | 3 to 4 inches, worked into the top 8 to 12 inches | Oregon State University Extension, EM 9308 How to Use Compost (2021) |
| Existing garden bed | ¼ to 1 inch a year | Oregon State University Extension, EM 9308 How to Use Compost (2021) |
| As mulch | 1 to 3 inches | Washington State University Extension, C075 Guide to Mulches |
| Raised bed fill | Up to 25% compost by volume, not compost alone | Oregon State University Extension, EM 9308 How to Use Compost (2021) |
Bags or bulk
Bagged compost usually comes in 1 or 2 cubic foot bags, and it suits smaller jobs. Bulk compost is sold by the cubic yard, and delivery is usually a flat fee.
Source: Oregon State University Extension, EM 9308 How to Use Compost (2021); Black Kow Organic Cow Manure Blend (1 cu ft bag); Coast of Maine Quoddy Blend Lobster Compost (1 and 2 cu ft bags)
Weight
Compost weighs 800 to more than 1,600 lb per cubic yard. Water makes the difference: about 1,000 lb is typical at 50% moisture.
Source: Oregon State University Extension, EM 9217 Interpreting Compost Analyses (2018); University of Minnesota Extension, Interpreting your compost report
Quick reference
| Depth | One cubic yard covers |
|---|---|
| 0.5 in | 648 sq ft |
| 1 in | 324 sq ft |
| 2 in | 162 sq ft |
| 3 in | 108 sq ft |
Questions people ask
How much compost do I need to topdress a lawn?
¼ to ½ inch. For 1,000 square feet at ½ inch, that is 1.54 cubic yards, or 42 bags of 1 cubic foot.
Source: Oregon State University Extension, EM 9308 How to Use Compost (2021)
How many bags of compost make a yard?
A cubic yard is 27 cubic feet: 27 bags of 1 cubic foot or 14 bags of 2 cubic feet.
How much area does a bag of compost cover?
A 1 cubic foot bag covers 12 square feet at 1 inch deep, or 24 square feet at ½ inch.
Source: Oregon State University Extension, EM 9308 How to Use Compost (2021); Black Kow Organic Cow Manure Blend (1 cu ft bag)
How much does a yard of compost weigh?
800 to more than 1,600 pounds, depending on how wet it is. About 1,000 pounds is typical for compost at 50% moisture.
Source: Oregon State University Extension, EM 9217 Interpreting Compost Analyses (2018)
Can I fill a raised bed with only compost?
No. Oregon State Extension advises up to 25% compost by volume, mixed with soil.
Source: Oregon State University Extension, EM 9308 How to Use Compost (2021)