Calculate C:N ratio and compost amounts from green and brown materials. Free online composting calculator with carbon-to-nitrogen ratio estimation.
The compost calculator helps you determine the carbon-to-nitrogen (C:N) ratio of your compost mixture and estimate the amount of finished compost you will produce. Achieving the right C:N ratio (25:1 to 35:1) is crucial for efficient decomposition, reducing odors, and producing nutrient-rich compost for your garden.
C:N Ratio = (Green × 20 + Brown × 60) ÷ (Green × 1 + Brown × 1)
Compost Yield = Total Material × 0.5
Volume (cu ft) = Yield (lbs) ÷ 40Green materials (kitchen scraps, grass clippings, manure) have a ~20:1 C:N ratio. Brown materials (leaves, straw, wood chips) have a ~60:1 C:N ratio. The ideal compost C:N ratio is 25:1-35:1. Compost typically reduces to 50% of its original volume during decomposition. Approximately 40 lbs of finished compost fills one cubic foot.
| Input | Output |
|---|---|
| 10 lbs green, 30 lbs brown, 5 cu ft needed | C:N 50:1 (too carbon-rich), ~20 lbs compost, ~0.5 cu ft |
| 20 lbs green, 30 lbs brown, 1 cu ft needed | C:N 40:1 (slightly carbon-rich), ~25 lbs compost, ~0.6 cu ft |
| 15 lbs green, 15 lbs brown, 1 cu ft needed | C:N 40:1 (slightly carbon-rich), ~15 lbs compost, ~0.4 cu ft |