Free Compost C:N Carbon to Nitrogen Calculator

Calculate exact weight ratios of brown (carbon) and green (nitrogen) organic inputs to hit the optimal 25:1 to 30:1 hot composting sweet spot.

🍂 Composting Raw Materials

Primary "Brown" Carbon Input

Weight of dry brown matter (lbs)

Primary "Green" Nitrogen Input

Weight of fresh green matter (lbs)

Target C:N Ratio

Pile Volume Goal

📊 Pile Ratio & Thermal Prediction

Current C:N Ratio 0 : 1 Status: Checking...

Estimated Peak Temp 0°F Thermophilic hot phase

Balance Adjustment Needed 0 lbs To hit target 30:1

Estimated Pile Moisture 0% Target: 45% - 60%

Decomposition Speed: Rapid Hot Compost (3 - 6 Weeks)

Weed Seed & Pathogen Kill: Achieved (>135°F for 3+ days)

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Frequently Asked Questions

Are coffee grounds considered a green or a brown in compost?

Even though they are brown in physical color, coffee grounds are classified as a GREEN with a rich C:N ratio of approximately 20:1 and about 2% nitrogen.

What is the "wrung-out sponge" rule for compost moisture?

Microbes require a thin water film to survive. Grab a handful of compost from the core of the pile and squeeze: only 1 or 2 drops of water should come out. If water streams out, it is too wet (>65% moisture); if it feels dry and dusty, add water.

How hot should a hot compost pile get?

An optimal hot compost pile reaches 135°F to 155°F (57°C to 68°C). Sustaining 135°F for 3 to 5 days kills weed seeds, fly larvae, and harmful plant pathogens.

Why do wood chips take so long to compost?

Fresh wood chips have a staggering C:N ratio of 400:1 to 500:1 and contain high levels of lignin, which only specialized white-rot and brown-rot fungi can enzymatically break down.