Formula used
Weekly food waste = entered waste × period conversion Suitable feed = weekly waste × suitable percentage Seasonal feed = suitable feed × seasonal adjustment Required worm mass = daily feed ÷ feeding rate × growth allowance Required surface area = weekly feed ÷ surface loading × safety factor Usable bin volume = physical volume × fill percentage Bedding volume = surface area × bedding depth × compaction allowance Bin utilisation = larger of surface or volume utilisation Bins required = ceiling of required capacity ÷ one-bin capacity Castings output = suitable feed × castings yield
How to use this calculator
Enter food scraps from a normal week. Exclude unsuitable materials before calculating. Use measured weights whenever possible.
Select your worm species and current biomass. Adjust feeding rates for local conditions. Conservative values reduce overfeeding risks.
Enter real internal bin dimensions. Include bedding and drainage depths. Review warnings before changing feeding routines.
Example data
| Scenario | Weekly scraps | Worm mass | Bin dimensions | Typical use |
|---|---|---|---|---|
| Small household | 2.5 kg | 1.0 kg | 45 × 35 × 30 cm | Light kitchen scraps |
| Average household | 4.5 kg | 1.5 kg | 60 × 40 × 35 cm | Regular family use |
| Large household | 8.0 kg | 3.0 kg | 80 × 50 × 40 cm | High weekly feed |
Practical guidance
Feed only after earlier scraps noticeably soften. Bury food under fresh bedding. Rotate feeding locations across the surface.
Keep bedding similar to a wrung sponge. Add dry cardboard when moisture rises. Improve drainage before adding more food.
Split crowded bins before severe competition begins. Move some bedding with each split. Keep both groups shaded and stable.
Frequently asked questions
How much can worms eat daily?
Healthy worms may process part of their body weight. Actual rates depend on temperature and bedding. Start below maximum estimates.
Why does surface area matter?
Composting worms mainly feed near the surface. Wider bins improve oxygen and access. Deep bins alone add limited capacity.
What bedding depth works best?
Many household bins use moderate bedding depths. Excess depth can trap moisture. Shallow bedding may dry too quickly.
Should leachate be expected?
Well-managed bins produce little free liquid. Excess leachate often indicates wet conditions. Correct moisture before increasing feed.
When should a bin be expanded?
Expansion is sensible near sustained capacity limits. Frequent uneaten food confirms overload. Split worms before conditions deteriorate.
Can different worm species share one bin?
Some species tolerate similar conditions. Temperature preferences can still differ. Use the stricter operating range.
Why include a safety factor?
Waste quantities change between weeks. Worm activity also changes seasonally. Extra capacity prevents sudden overloads.
How accurate is the castings estimate?
Castings yield varies with feed and harvesting. Bedding also becomes processed material. Treat output as a planning estimate.
Can this calculator size commercial systems?
It supports larger values and multiple bins. Commercial systems need site testing. Confirm airflow, labour, and feed consistency.
What food should be excluded?
Avoid large amounts of oils and salty foods. Limit meat and dairy indoors. Follow local vermiculture guidance.
Why might processing time exceed seven days?
The current worm mass may be insufficient. Cool conditions can also slow feeding. Reduce inputs until capacity improves.