GARDEN FIELD BOOK / CALCULATOR 08
Compost Application Calculator
Enter your garden area and the compost depth you plan to apply. Calculate a new layer or a measured top-up, then compare cubic feet, cubic yards, liters and bag counts. The calculator does not choose a compost application depth for you.
100 ft² covered by a layer 1 inch deep
0.309 cubic yards of compost
YOUR MEASUREMENTS
Set area and application depth
VOLUME & PACKAGING
Your compost estimate
The result separates the measured compost layer from any optional purchase allowance.
Whole bags
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BEFORE YOU CALCULATE
Measure the surface, then choose the compost layer
Use the actual growing area
Enter the garden area you plan to cover. Exclude spaces not receiving compost. For irregular beds, measure sections separately and combine the areas.
Enter your chosen thickness
Depth controls volume directly. This calculator does not select an application rate or determine whether your soil needs additional organic matter.
Account for existing compost only
Choose Top-up only for an existing compost layer with known thickness. The new quantity uses the positive difference between your target and the current layer.
HOW THE CALCULATOR WORKS
Compost volume uses area × thickness
For example, covering 100 square feet with a measured layer 1 inch deep requires about 8.33 cubic feet, or 0.309 cubic yards. At 2 cubic feet per bag with no extra allowance, that rounds up to 5 bags. These figures describe volume, not weight or nutrient content.
Measurements are geometric estimates. Irregular surfaces, uncompacted bag volumes and material variation can affect how much compost you actually use. The optional percentage applies only to estimated purchase volume.
READ THE RESULT CORRECTLY
What this calculation cannot decide
It does not tell you whether compost is needed
Compost quality, soluble salts, crops, current soil conditions and existing organic matter may change the appropriate application decision.
It does not calculate nutrient delivery
Compost composition varies. Volume alone cannot predict nitrogen, phosphorus or potassium availability.
Use the right calculation for the job
A surface compost layer is different from filling an empty raised bed with soil or topping up wood-chip mulch. Those are separate material decisions.
CONTINUE PLANNING
Useful garden guides
Find more practical tools in the Garden Calculators & Planning Tools directory.