Formula used
Weekly waste: entered waste is converted into kilograms per week. Growth and safety assumptions are then applied. This creates one consistent planning basis.
Recommended worms: daily waste ÷ selected feeding rate. Safety and mortality allowances increase the starting estimate. New bins should still increase feeding gradually.
Bin volume: weekly waste × retention weeks ÷ bulk density. The usable-depth percentage converts usable space into total volume. A safety margin prevents immediate overfilling.
Moisture correction: water or dry bedding is added mathematically. The calculation balances present and target moisture percentages. Apply changes slowly while mixing thoroughly.
Yield: projected input × selected yield percentage × environment factor. Finished volume uses the chosen bulk density. Real harvests vary between systems.
How to use this calculator
- Enter the organic waste produced daily or weekly.
- Select worm species and conservative feeding capacity.
- Use automatic bin sizing or enter existing dimensions.
- Set bedding, moisture, carbon, and temperature assumptions.
- Choose a projection period and expected finished yield.
- Enter the planned garden or potting application.
- Add costs to estimate value and payback.
- Calculate, review warnings, and adjust the plan.
Example data
| Scenario | Waste | Worms | Bin approach | Projection |
|---|---|---|---|---|
| Small household | 5 kg/week | About 1.6 kg | One medium bin | 12 weeks |
| Large household | 12 kg/week | About 3.8 kg | Two-bin rotation | 16 weeks |
| School project | 30 kg/week | About 9.5 kg | Multiple managed bins | 20 weeks |
| Farm trial | 75 kg/week | About 24 kg | Modular beds | 26 weeks |
Vermicomposting guidance
Composting worms thrive in moist, airy bedding with regular food. Feed should be buried beneath a dry carbon cover. This helps reduce flies and odours.
Do not treat the calculated feeding allowance as a fixed command. Worm activity changes with temperature, moisture, and population size. Add more food only after previous material breaks down.
Finished castings are usually dark, granular, and earthy smelling. Separate worms before storing or applying the material. Avoid waterlogged storage without airflow.
Raw bin drainage is not automatically safe finished worm tea. It may contain anaerobic organisms or dissolved compounds. Use cautious handling and local guidance.
Frequently asked questions
Which worms work best?
Red wigglers are widely used because they live near the surface. They reproduce quickly under suitable conditions. Local availability and climate still matter.
Can earthworms from garden soil be used?
Many soil worms need deeper mineral soil than a worm bin. Composting species tolerate dense organic bedding better. Use a known composting species whenever possible.
How much food can worms eat?
Feeding rates vary widely with conditions and worm maturity. Conservative plans often start below theoretical capacity. Increase feed only after observing reliable processing.
What moisture level is suitable?
Moist bedding should feel similar to a wrung-out sponge. Standing liquid suggests excessive moisture or poor drainage. Dry bedding slows feeding and reproduction.
Why does the bin smell?
Odour often indicates overfeeding, compaction, or excess moisture. Remove spoiled food and add dry bedding. Improve airflow without drying the system completely.
How often should bedding be added?
Add bedding whenever feed becomes exposed or the bin compacts. Keep fresh carbon material available for moisture correction. Regular small additions are easier to manage.
When is vermicompost ready?
Finished material becomes dark, fine, and earthy smelling. Recognisable feed should be limited. Harvest timing depends on temperature and feeding rates.
Can citrus and onions be added?
Small amounts may be tolerated in established systems. Large acidic additions can stress worms. Mix them with other feed and monitor carefully.
Should leachate be used on plants?
Raw drainage differs from prepared aerated worm tea. Its quality and microbial content are uncertain. Dilute cautiously or avoid application to edible leaves.
Are calculator results guaranteed?
No calculation can capture every biological and environmental variable. Use the output for planning and comparison. Let actual worm activity guide final decisions.