Garden Compost Calculator
Determine exactly how much compost your garden beds or lawn requires.
How to Use the Compost Calculator
Providing your soil with organic matter is the single best way to improve plant health. This calculator helps you avoid over-purchasing or running short in the middle of a project. To use it, simply select the shape of your garden bed, input the dimensions in feet, and choose your desired depth. Most seasonal top-dressing requires 1 to 2 inches, while new garden beds may require up to 4 inches of compost mixed into the existing soil.
Why Depth Matters
The amount of compost you apply depends on your goal:
| Application | Recommended Depth |
|---|---|
| Existing Lawn Top-Dressing | 0.25 to 0.5 inches |
| Annual Flower Beds | 1 to 2 inches |
| New Vegetable Gardens | 3 to 4 inches |
| Erosion Control | 2 to 3 inches |
Manual Calculation Formula
If you prefer to calculate by hand, the formula for a rectangular area is:
(Length in feet × Width in feet × (Depth in inches / 12)) / 27 = Total Cubic Yards
Since there are 27 cubic feet in one cubic yard, we divide the total cubic feet by 27 to get the standard measurement used by bulk landscaping suppliers.
Example Calculation
Suppose you have a raised vegetable bed that is 8 feet long and 4 feet wide. You want to add 3 inches of high-quality organic compost to prepare for the spring planting season.
- Square Footage: 8 ft × 4 ft = 32 sq. ft.
- Depth in Feet: 3 inches / 12 = 0.25 ft.
- Cubic Feet: 32 sq. ft. × 0.25 ft = 8 cubic feet.
- Cubic Yards: 8 / 27 = 0.29 cubic yards.
In this scenario, you would need approximately 8 bags (if using standard 1-cubic-foot bags) or roughly one-third of a cubic yard if ordering in bulk.