Compost Ratio Calculator - Free Online Calculator Tool

Quick Answer

The Compost Ratio Calculator helps achieve the ideal 25-30:1 carbon-to-nitrogen (C:N) ratio for efficient composting, preventing slow decomposition or foul odors.[2] Input weights of greens (nitrogen-rich like food scraps) and browns (carbon-rich like leaves) for precise recipes that speed up breakdown and divert up to 520 pounds of household waste yearly.[1][6]

Why You Need This

Imbalanced compost piles fail: high C:N ratios (>30:1) slow decomposition, while low ratios (<20:1) cause rotting, ammonia release, and odors.[2] Common in home gardens, this leads to nutrient mismatches like excess phosphorus in soil, exceeding environmental thresholds when used as a primary nitrogen source.[1][3] U.S. households could divert significant landfill waste—10 pounds weekly equals 520 pounds annually—but ratio errors reduce success.[6] Manures vary widely (7-53:1 C:N, e.g., turkey at 9:1, sheep at 25:1), needing browns for balance and 20-40% volume reduction.[4] Home gardeners, farmers, and worm farmers benefit most by matching crop needs and cutting methane emissions.[5]

How It Works

Select materials from dropdowns (e.g., coffee grounds, sawdust, manure), enter weights (not volumes, as densities differ—3 gallons sawdust out-carbons dry leaves).[2] The calculator computes total C:N ratio, moisture, and bulk density, targeting 25-30:1 for hot composting (150°F+).[1][2] Adjust iteratively for vermicomposting (40-50:1) or standard piles.[4]

Tips for Best Results

• Use weights and known C:N values; mix particle sizes (e.g., wood chips with grounds) for aeration.[2]
• Aim for 1-2 inches compost annually, blended 25-30% into 6-8 inches soil; test soil to limit phosphorus.[3][5]
• Monitor heat (150°F+), no odors, and maturity (<20:1 C:N) for yields, better water retention, and less fertilizer.[1] Composting reduces manure 20-40% while optimizing nutrients.[4]

Sources

• treefruit.wsu.edu
• urbanwormcompany.com
• extension.psu.edu
• extension.usu.edu
• epa.gov