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Calcimator

Compost Ratio Calculator

Calculate your compost C:N ratio from green and brown materials. Get quality assessment and adjustment suggestions for optimal decomposition.

Inputs

cu ft
cu ft

Results

C:N Ratio

48.8:1

Quality AssessmentToo Much Carbon
Adjustment SuggestionAdd more green material. Try adding 30 cu ft of green material to reach a 30:1 ratio.
Total Material Volume20 cu ft
Green:Brown Volume Ratio0.33:1
Est. Finished Compost8 cu ft
Est. Decomposition Time24 weeks
How to Use This Calculator
  1. Measure or estimate the volume of your green (nitrogen-rich) materials in cubic feet — grass clippings, kitchen scraps, or fresh manure.
  2. Select the green material type that best matches your pile contents to apply the correct C:N ratio.
  3. Enter the volume of your brown (carbon-rich) materials — dry leaves, straw, cardboard, or wood chips.
  4. Choose the brown material type so the calculator can compute the weighted average C:N ratio.
  5. Review the C:N Ratio and Quality Assessment outputs — the ideal range is 25:1 to 35:1 for fast decomposition.
  6. Follow the Adjustment Suggestion to add more greens or browns, then check the estimated decomposition time and finished compost volume.

How the result changes with Green Material Volume

Green Material VolumeC:N Ratio
5025.4:1
17518.6:1
32517:1
45016.5:1

What each input means

Green Material Volume
Volume of nitrogen-rich green materials in cubic feet.
Green Material Type
Primary type of green (nitrogen-rich) material being composted.
Brown Material Volume
Volume of carbon-rich brown materials in cubic feet.
Brown Material Type
Primary type of brown (carbon-rich) material being composted.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Green Material Volume = 5, Green Material Type = 1, Brown Material Volume = 15, Brown Material Type = 1 = 4 input(s) provided
  2. Calculate C:N Ratio
    C:N Ratio
    48.8 = 48.8
  3. Calculate Quality Assessment
    Too Much Carbon = Too Much Carbon
  4. Calculate Adjustment Suggestion
    Add more green material. Try adding 30 cu ft of green material to reach a 30:1 ratio. = Add more green material. Try adding 30 cu ft of green material to reach a 30:1 ratio.

Engine last updated . Checked against 1 independently-derived test — how we verify calculators.

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