GardenCalcs.uk
Compost Bin Size Calculator — What Size Compost Bin Do I Need
Work out the ideal compost bin size for your garden and kitchen waste.
Garden waste = prunings, grass, leaves; kitchen = uncooked peelings and scraps. Combine both for a mixed home heap.
Total area producing clippings, weeds and prunings — beds, borders and lawn, not paving or buildings.
People producing compostable kitchen scraps. Drives the kitchen-waste portion only.
Garden waste per m² per week (default 0.5)
Kitchen waste per person per week (default 3)
Months for compost to mature (default 6)
Usable bin fraction for aeration (default 0.7 = 70%)
Common compost bin capacity (default 330 L)
How We Calculate This
This calculator estimates your weekly organic waste output based on garden size and household members.
Garden waste is estimated at ~0.5 litres per m² per week (averaged over the year). Kitchen waste is roughly 3 litres per person per week.
The recommended capacity sizes the bin over the maturation period at 70% fill (leaving room for turning and aeration), but applies a ~50% volume-retention factor: compost shrinks 30-50% as it breaks down and waste is added continuously, so the bin only ever holds a fraction of the total fresh waste you add over the cycle.
The compost yield is the annual harvest, calculated as ~40% of a full year's raw input — finished compost volume is roughly 40-50% of the feedstock that went in.
Frequently Asked Questions
A small garden (around 20 m²) plus a couple of people’s kitchen scraps composts happily in a single 330-litre converter. A typical 50 m² garden plus household waste fills the equivalent of two 330-litre bins over a 6-month cycle, so most people run a two-bin rotation — one filling while the other matures. Remember compost shrinks 30-50% as it breaks down, so the bin needs far less capacity than the total fresh waste you add.
In a well-managed bin, compost can be ready in 6-12 months. Hot composting can produce usable compost in as little as 8-12 weeks.
Having two bins is ideal: one to fill while the other matures. This gives you a continuous supply of finished compost.
Green materials: fruit and veg peelings, grass clippings, tea bags. Brown materials: cardboard, dry leaves, woody prunings, paper. Avoid meat, dairy, and cooked food.
A well-managed hot compost bin produces usable compost in 8-12 weeks. Cold composting takes 6-12 months. Turning regularly and balancing green/brown materials speeds things up.
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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.