Compost recipe calculator - greens vs browns ratio
Tell us what materials you have. We'll calculate the right ratio of browns to greens (target C:N ratio around 25-30:1) and tell you what to add to make a hot pile that actually breaks down.
Free · No signup · Based on Cornell Composting and Penn State ExtensionWhat you have
Enter rough volume in 5-gallon buckets (or any consistent unit - the ratio is what matters).
GREENS (high nitrogen)
BROWNS (high carbon)
What the ratio actually means
Compost piles need a balance of carbon (browns) and nitrogen (greens). The ideal carbon-to-nitrogen ratio is 25-30:1 by weight. Volume-wise that translates roughly to 2-3 parts browns to 1 part greens for a typical mix of materials.
Per Cornell Composting, when the ratio is right, a properly built pile heats to 130-150F within a week, kills weed seeds and pathogens, and breaks down in 6-12 weeks.
Too many greens (ratio below 20:1) means a smelly, slimy, anaerobic pile. Too many browns (above 40:1) means a pile that just sits and doesn't heat up.
Beyond the ratio, three other things matter: moisture (wrung-out sponge), particle size (smaller breaks down faster), and aeration (turn every 1-2 weeks).
Per Penn State Extension's composting guide, hot composting requires a minimum pile volume of 27 cubic feet (3x3x3) to retain heat. Smaller piles work but break down more slowly via cold composting.