What is the ideal green to brown ratio?

By volume, aim for roughly 1 part green to 2-3 parts brown. By weight, the optimal carbon-to-nitrogen ratio is 25-30:1. Volume ratio is easier to judge in practice.

What counts as green material?

Greens are nitrogen-rich: grass clippings, fruit/veg peelings, coffee grounds, fresh plant trimmings, and weeds (without seeds).

What counts as brown material?

Browns are carbon-rich: dry leaves, cardboard, newspaper, straw, wood chips, sawdust, and dry garden stalks.

My compost is slimy and smells, what should I do?

Add more brown materials and turn the heap. Slimy, smelly compost has too much nitrogen (green) and not enough carbon (brown) and airflow.

Can I compost cooked food?

Avoid cooked food, meat, and dairy in open compost heaps as they attract rats. These can go in a sealed hot composter or Bokashi bin, then be added to compost.

GardenCalcs

Green to Brown Ratio Calculator — Compost Balance

Balance green and brown materials for optimal composting.

Green Materials (litres per week)

Grass Clippings

Kitchen Scraps

Fresh Leaves/Weeds

Brown Materials (litres per week)

Dry Leaves

Cardboard/Paper

Woody Prunings

Straw

How We Calculate This

This calculator totals your green (nitrogen-rich) and brown (carbon-rich) materials by volume, then checks the ratio against composting best practice.

The ideal ratio by volume is 1 part green to 2-3 parts brown. This typically produces the 25-30:1 carbon-to-nitrogen ratio that microbes need for efficient decomposition.

Too much green = wet, slimy, anaerobic compost. Too much brown = dry, slow decomposition.

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.