Compost Ratio Calculator
Balance your compost pile with the right brown-to-green ratio.
Calculate volumes of carbon and nitrogen materials needed.
Compost Recipe
Successful composting depends on the right balance of carbon-rich “brown” materials and nitrogen-rich “green” materials.
The ideal carbon-to-nitrogen (C:N) ratio is approximately 25:1 to 30:1. This ratio provides the optimal environment for decomposition microorganisms.
Why the ratio matters:
- Too much carbon (too many browns): Decomposition slows dramatically. The pile may sit for months with little change.
- Too much nitrogen (too many greens): The pile becomes slimy, compacted, and smelly (ammonia odor).
- Just right: The pile heats up quickly, breaks down efficiently, and produces rich, dark compost.
Common brown materials (carbon-rich):
- Dry leaves: C:N ratio ~60:1
- Straw: C:N ratio ~75:1
- Cardboard: C:N ratio ~350:1
- Wood chips: C:N ratio ~400:1
- Newspaper: C:N ratio ~175:1
- Sawdust: C:N ratio ~325:1
Common green materials (nitrogen-rich):
- Grass clippings: C:N ratio ~17:1
- Kitchen scraps (fruit/veg): C:N ratio ~15:1
- Coffee grounds: C:N ratio ~20:1
- Fresh garden waste: C:N ratio ~25:1
- Manure (herbivore): C:N ratio ~15:1
Volume rule of thumb: Since browns are much higher in carbon per unit than greens are in nitrogen, the volume ratio works out to roughly 3 parts brown to 1 part green by volume for most common materials.
Additional requirements:
- Moisture: The pile should feel like a wrung-out sponge.
- Air: Turn the pile every 1-2 weeks to introduce oxygen.
- Size: Minimum 3×3×3 feet (1×1×1 m) to generate enough heat.