Worm Castings Calculator

Enter your garden area and application rate to find the worm castings needed.

How to use

  1. Enter your values in the fields above.
  2. Press Calculate to see your result instantly.
  3. Use the Share button to copy a link to your result.

About this calculator

Worm castings — the nutrient-rich excrement produced by vermicomposting worms — are a slow-release organic soil amendment prized for improving soil structure, water retention and microbial activity without the burn risk of synthetic fertilizer. Because they’re applied by weight relative to bed area, typical application rates are expressed as pounds per square foot of garden bed.

This calculator takes your garden bed’s area and a chosen application rate to estimate how many pounds (and kilograms) of castings you need, plus how many standard 40 lb bags to buy. It’s a practical planning step for organic and home gardeners amending vegetable beds or raised beds, and for anyone running a vermicomposting operation figuring out how much of their harvested castings a given planting area will actually use.

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