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Vermicompost Calculator
Size your earthworm population and predict vermicompost yield based on daily waste input, waste type (which sets conversion efficiency) and target production.
Results
How to Use This Calculator
Enter your daily food waste in kg, your current worm count, the waste type (fruit/veg scraps are high-N, paper/cardboard is high-C, mixed is balanced) and target monthly vermicompost. Click Calculate.
About This Tool
Red wiggler worms (Eisenia fetida) consume roughly their own weight in organic matter per day. A population of 1,000 worms weighs about 1 kg. Vermicompost yield is typically 20–30% of input weight (30–40% for optimal conditions).
Applicability: Applicable globally, with particular relevance for North American and European cropping systems. Adapt rates to your soil test results.
How the Calculation Works
Worms needed = waste (kg/day) × 1,000. Monthly yield (kg) = waste (kg/day) × 30 × yield fraction (0.1–0.3). Time to target = target ÷ monthly yield. C:N adjustment is suggested when the input is skewed to one side.
Real-World Example
1 kg/day mixed waste, current 1,000 worms, target 10 kg/month. Worms needed = 1,000 (matches). Monthly yield = 1 × 30 × 0.2 = 6 kg. Time to 10 kg ≈ 1.7 months.
Common Mistakes & Tips
Common mistakes: overfeeding (the #1 cause of bin odor), keeping worms too cold or too hot (optimal 15–25 °C), adding meat/dairy/oil (attracts pests), not bedding with shredded cardboard, and expecting fast population growth (worms double in 2–3 months under ideal conditions).
Reviewed by Agricalc Editorial Team — Agricultural engineers and agronomists with 10+ years of field experience. Our team verifies every calculator formula against peer-reviewed extension publications. For site-specific advice, consult your local agronomist.
References
Frequently Asked Questions
How many worms do I need?
As a rule of thumb, ~1,000 red wigglers (about 1 kg) process 1 kg of food waste per day. For a household producing 1 kg/day, start with 1,000–2,000 worms and let the population grow. Buy worms by weight, not count, when possible.
What is vermicompost yield?
About 20–30% of the feed weight becomes finished vermicompost. 10 kg of food scraps over a month yields 2–3 kg of worm castings. The rest is lost as CO₂ and water vapor.
What can I feed worms?
Fruit and vegetable scraps, coffee grounds (with filter), tea bags, crushed eggshells, shredded paper and cardboard are ideal. Avoid meat, dairy, oily foods, citrus in large amounts, onions and spicy foods. Do not overfeed — bury food under bedding.
How do I harvest vermicompost?
Move all bedding to one side of the bin, add fresh bedding and food to the empty side. After 2–4 weeks most worms migrate to the fresh side; scoop castings from the other side. The light method: shine a lamp on the pile; worms dive down, allowing top layer scraping.
What temperature is best?
Red wigglers prefer 15–25 °C (60–77 °F). Below 10 °C they slow down; above 30 °C they die. Keep bins in shade in summer, insulated in winter. Bedding should feel like a wrung-out sponge — moist but not soggy.
