Compost Calculator
Enter the length, width, and desired depth of your garden bed or application area to estimate how much compost you'll need.
Last updated: September 25, 2026
Frequently asked questions
How much compost do I need for a 20×10 ft bed at 2 inches deep?
20×10 ft is 200 sq ft. At 2 inches deep that's about 33.3 cubic feet, or roughly 1.23 cubic yards - about 22 bags of 1.5 cu ft compost.
How deep should a compost layer be?
It depends on the purpose - a 1-3 inch layer is typical for amending or top-dressing existing garden soil, while new beds or heavily depleted soil sometimes use a thicker 3-4 inch layer worked into the top several inches of native soil.
What's the difference between this and the Mulch Calculator?
Both estimate a volume from area and depth using the same underlying math, but they serve different materials and purposes - compost is a soil amendment worked into or laid over soil to add nutrients and organic matter, while mulch is typically a surface layer (bark, wood chips, etc.) used mainly for weed suppression and moisture retention. Use whichever calculator matches the material you're actually applying.
Should I mix compost into the soil or just spread it on top?
Both are common depending on the situation - working compost into the top several inches of soil is typical when preparing a new bed, while top-dressing (spreading a layer on the surface without digging it in) is common for established plantings and lawns, where compost breaks down gradually and works its way in over time.
How many bags of compost equal a cubic yard?
It depends on the bag size, which varies by brand and product - a common bag size is around 1-2 cubic feet, and since a cubic yard is 27 cubic feet, that works out to roughly 14-27 bags per cubic yard. Enter your specific bag's volume in the calculator for an accurate bag count.
Does this calculator account for compost settling over time?
Not directly - like most volume estimates, it calculates the freshly applied volume. Compost, especially less mature compost, can settle and decompose further after application, so some gardeners apply slightly more than the calculated minimum or plan to top up over time.