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Size your earthworm population and predict vermicompost yield based on daily waste input, waste type (which sets conversion efficiency) and target production.
Enter daily waste input, current worm count, waste type and target vermicompost production. The calculator returns worms needed, capacity check, monthly yield and C:N adjustment advice.
You bought 1,000 red wigglers and started feeding them 3 kg of kitchen scraps a day. Within a week the bin smelled rotten and flies appeared. Red wigglers process about their own weight per day — 1,000 worms weigh ~1 kg and can handle ~1 kg of food, not 3 kg.
✓ Expert Reviewed: This calculator and its content have been reviewed by agricultural experts. Formulas are based on standard extension service recommendations. For site-specific advice, consult your local agronomist.
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.
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).
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.
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: 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).
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.
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.
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.
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.
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.