What is the ideal carbon to nitrogen ratio for compost?

The ideal C:N ratio for active composting is between 25:1 and 30:1. Below 20:1 (too much nitrogen), your pile may smell like ammonia. Above 40:1 (too much carbon), decomposition slows significantly. Achieving the right balance is the single most important factor for fast, odor-free composting.

What can I put in my compost bin?

Greens (nitrogen sources): grass clippings, vegetable scraps, coffee grounds, fresh manure, and green leaves. Browns (carbon sources): dry leaves, straw, cardboard, wood chips, sawdust, and newspaper. Avoid meat, dairy, oily foods, diseased plants, and pet waste, as these attract pests or introduce pathogens.

How long does composting take?

Hot composting (actively managed, turned regularly, correct C:N ratio) takes 4–8 weeks. Cold composting (passive, minimal turning) takes 3–6 months or longer. The key factors are C:N ratio, moisture (should feel like a wrung-out sponge), aeration (turn every 1–2 weeks), and particle size (smaller pieces decompose faster).

Why does my compost smell bad?

A rotten egg smell usually means the pile is too wet and anaerobic — turn it and add dry browns. An ammonia smell means too much nitrogen (greens) — add more carbon-rich browns like dry leaves or cardboard. A well-balanced, properly aerated compost pile should smell earthy, not unpleasant.

Compost Calculator

Calculate your compost C:N ratio, bin volume, and get balancing recommendations.

Bin Dimensions

Length (ft)

Width (ft)

Height (ft)

Materials

lbs

How to Use

Enter your compost bin dimensions (length, width, height).
Add your compost materials using the material selector — choose from greens (nitrogen-rich) and browns (carbon-rich).
Enter the weight or volume of each material you plan to add.
Click Calculate to see your current C:N ratio and whether you need more greens or browns.
Follow the balancing recommendation to reach the ideal 25:1–30:1 ratio for fast composting.

Frequently Asked Questions

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