Vermicompost Calculator

Vermicomposting uses specific species of earthworms (most commonly red wigglers, Eisenia fetida) to break down organic kitchen waste into nutrient-rich compost called vermicast or worm castings. It is an efficient, odorless composting method suitable for apartments and homes.

The fundamental calculation: Red wiggler worms consume approximately half their body weight in food scraps per day under ideal conditions. This means:

Worms Needed (lbs) = Daily Food Waste (lbs) / 0.5

Or equivalently, one pound of red wigglers can process about 3.5 pounds of food waste per week.

Worm bin sizing: The bin should provide approximately 1 square foot of surface area per pound of food waste per week. Depth should be 8-12 inches (20-30 cm). Worms feed primarily in the top few inches.

Bin Surface Area (sq ft) = Weekly Food Waste (lbs)

For a household producing 3.5 pounds of food waste per week, a bin approximately 2 feet × 2 feet (4 square feet) provides adequate space.

How many worms to start:

• One pound of red wigglers contains approximately 800-1,000 worms
• A typical starting quantity is 1-2 pounds for a household bin
• Worms will naturally regulate their population to match the food supply
• Under ideal conditions, worms can double their population in about 90 days

Bedding materials: The bin needs carbon-rich bedding material that retains moisture and allows air flow. Suitable materials include shredded newspaper, cardboard, coconut coir, and aged leaves. Maintain a bedding-to-food ratio of approximately 3:1 by volume.

Ideal conditions:

• Temperature: 55-77°F (13-25°C). Red wigglers thrive at about 68°F (20°C).
• Moisture: 70-80% (bedding should feel like a wrung-out sponge)
• pH: 6.0-7.0 (neutral to slightly acidic)
• Darkness: Worms avoid light, so keep the bin covered

What to feed worms: Fruit and vegetable scraps, coffee grounds and filters, tea bags, crushed eggshells, bread in small amounts. Avoid citrus in large quantities, onions, garlic, meat, dairy, oils, and pet waste.

Harvesting vermicompost: After 3-6 months, the bottom of the bin will contain dark, earthy-smelling vermicast ready for use. The most common harvesting method is to push the finished compost to one side and add fresh bedding and food to the other side. Worms will migrate toward the food within 2-3 weeks, allowing you to collect the finished compost.

Vermicompost benefits: Worm castings contain 5 times the nitrogen, 7 times the phosphorus, and 11 times the potassium of regular garden soil. They also contain beneficial microorganisms that improve soil structure and plant health.