How many worms do I need?

A general rule is 2,000 worms per kg of daily food waste. For a household of 2, producing about 0.85 kg/day, you would need roughly 1,700 worms (about 500g).

What worms should I use?

Use composting worms (Eisenia fetida or Dendrobaena veneta), not earthworms. They are surface feeders that thrive in decomposing organic matter.

How fast do composting worms multiply?

Composting worms can double their population every 3-4 months under ideal conditions. Start with fewer worms and the colony will grow to match food supply.

What can I feed composting worms?

Fruit and veg scraps, tea bags, coffee grounds, cardboard, and paper. Avoid citrus, onion, meat, dairy, and oily foods.

What kind of worms do I need?

Brandling worms (Eisenia fetida) are best for wormeries. They are red/tiger striped and available from garden centres. Do not use common earthworms as they prefer deeper soil.

GardenCalcs

Worm Composting Calculator — Wormery Size Guide

Calculate wormery size and worm quantities for your food waste.

Household Size

Weekly Waste per Person

Average UK household: 2-4 kg/person/week

How We Calculate This

Composting worms eat roughly half their body weight in food waste per day. An average worm weighs about 0.5g, so 2,000 worms process about 0.5 kg of waste daily.

Formula: Worms needed = Daily waste (kg) × 2,000

Bin size is based on approximately 0.5 cm² surface area per worm for comfortable conditions. Worm castings output is approximately 60% of input weight.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates based on standard gardening guidelines. Results may vary with soil conditions, climate, and plant varieties.