Compost Carbon-to-Nitrogen (C:N) Ratio Calculator

Compost C:N Blend

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Target {{ targetRangeLabel }}

Measurement system:

Target ratio minimum:

: 1

Target ratio maximum:

: 1

Account for moisture:

Materials

Start with balanced mix: browns such as leaves or straw deliver carbon, greens like food scraps and manure deliver nitrogen. Ratio and moisture values are editable.

Add your first material to start calculating the blend.

Material {{ index + 1 }}

Preset:

Name:

C:N ratio:

: 1

Moisture:

Water is removed before blending so ratios reflect dry matter.

Weight:

Metric	Value	Copy
{{ row.label }}	{{ row.value }}

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Material	C:N	Wet weight	Dry weight	Carbon	Nitrogen	Copy
{{ row.label }}	{{ row.ratioDisplay }}	{{ row.wetWeightDisplay }}	{{ row.dryWeightDisplay }}	{{ row.carbonDisplay }}	{{ row.nitrogenDisplay }}

Carbon and nitrogen totals are dry-matter estimates. Moisture loss reflects the share of water removed before blending.

Add at least one material to chart dry mass distribution.

Add at least one material to chart carbon and nitrogen contributions.

Add materials to generate the mass components chart.

Add your brown and green ingredients to see the blended C:N ratio and guidance for balancing the pile.

Tags: Education , Gardening , Productivity

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Carbon to nitrogen ratio is a simple way to describe the balance between dry browns and wet greens in a compost blend. Getting this balance close helps a pile heat well and finish faster with fewer odors.

You enter a few materials with their carbon to nitrogen ratios, moisture estimates, and weights, then see a blended ratio for the whole mix. The tool also explains whether the result sits inside your target band and suggests which side needs attention when it does not.

A quick scenario might combine dry leaves with kitchen scraps and fresh grass, then show a result near the hot compost window so you can proceed with confidence. If the number drifts low, add browns; if it climbs high, add greens.

Numbers improve when moisture is estimated consistently and weights use the same unit for every ingredient. Be wary of unusually extreme ratios, since those can pull the blend in ways that do not reflect your actual pile.

Technical Details:

The calculator models dry matter for each ingredient, then apportions that dry matter into carbon and nitrogen according to its stated carbon to nitrogen ratio. Results summarize totals, a final blended ratio, and a simple classification against a user set band.

Each ingredient contributes a wet mass, a moisture fraction, and a ratio. Moisture is removed first to obtain dry mass, because ratios refer to dry material rather than water weight. Carbon and nitrogen shares are then derived from the ratio parts.

Classification describes three cases. Values below the lower bound are nitrogen heavy, values above the upper bound are carbon heavy, and values that land within the band are balanced. Values near edges should be read with care and confirmed after a first turn.

Comparisons are most meaningful within a single project using consistent moisture assumptions and similar particle sizes. The model does not infer pile temperature or decomposition rate; it reports a mass based balance only.

\begin{array}{l} M_{d, i} = M_{w, i} (1 - m_{i}) \\ C_{i} = M_{d, i} \frac{R_{i}}{R_{i} + 1} \\ N_{i} = M_{d, i} \frac{1}{R_{i} + 1} \end{array}

R = \frac{\sum C_{i}}{\sum N_{i}}

Symbols and units
Symbol	Meaning	Unit/Datatype	Source
Ri	Ingredient carbon to nitrogen ratio	ratio	Input
Mw,i	Wet mass	kg or lb	Input
mi	Moisture fraction	0 to 1	Input
Md,i	Dry mass	kg or lb	Derived
Ci	Carbon mass share	kg or lb	Derived
Ni	Nitrogen mass share	kg or lb	Derived
R	Final blended ratio	ratio	Derived

Worked example.

Ingredients: dry leaves 20 lb at 10% moisture, kitchen scraps 12 lb at 70% moisture, fresh grass 12 lb at 70% moisture.

\begin{array}{l} Leaves : R_{i} = 60, M_{w} = 20 lb \\ Scraps : R_{i} = 15, M_{w} = 12 lb \\ Grass : R_{i} = 17, M_{w} = 12 lb \end{array}

After unit conversion and moisture removal: dry leaves ≈ 8.1647 kg, scraps ≈ 1.6329 kg, grass ≈ 1.6329 kg.

\begin{array}{l} \sum C_{i} \approx 11.1039 kg \\ \sum N_{i} \approx 0.3266 kg \\ R \approx 34.0 : 1 \end{array}

With a 25 to 35 target band, the blend is balanced. Estimated moisture loss is about 42.7% of wet weight.

Interpretation bands
Band	Lower bound	Upper bound	Interpretation	Action cue
Balanced	User set	User set	Blend lands inside the window.	Maintain moisture and turn regularly.
Nitrogen heavy	Below lower	—	Too rich in greens.	Add browns to raise the ratio.
Carbon heavy	—	Above upper	Too rich in browns.	Add greens to lower the ratio.

Units, precision, and rounding

Weights display in kilograms or pounds. The unit toggle converts entered weights and rounds to three decimal places. Display precision adapts to magnitude: two decimals below 10, one between 10 and 100, and none at 100 or above. Final ratios display to one decimal.

Validation and bounds

Validation rules
Field	Type	Min	Max	Step/Pattern	Error text
Target ratio minimum	Number	5	100	1	Band must be greater than zero and maximum must exceed minimum.
Target ratio maximum	Number	10	80	1	Band must be greater than zero and maximum must exceed minimum.
Ingredient ratio	Number	5	600	1	Enter a value greater than zero.
Moisture	Number	0	90	1	When enabled, moisture must be between 0 and 99.
Weight	Number	0.1	—	0.1	Needs a weight greater than zero.

I/O formats

Inputs and outputs
Input	Accepted families	Output	Encoding/precision	Rounding
Numbers	Integers and decimals	On‑screen tables	Adaptive decimals	Banker’s rounding not used; standard toFixed.
Summary export	Copy or download	CSV, JSON	Escapes quotes, highlights JSON	As displayed

Networking & privacy

Processing is client‑only and no network requests are made. Clipboard and file downloads use standard browser capabilities. No data is transmitted or stored server‑side.

Assumptions & limitations

Ratios describe dry matter; water is excluded from balance calculations.
Moisture is user estimated; errors propagate to results. Heads‑up
Presets are starting points and may not match local materials.
The model does not infer temperature, airflow, or particle size.
Classification reflects your chosen band only.
No volume to weight conversion is attempted.
Extremely high or low ratios can dominate totals.
Unit toggles convert existing entries and round to three decimals.

Edge cases & error sources

Empty material list prevents calculation.
Zero or negative weights are invalid.
Ratios at or below zero are invalid.
Moisture at 100% removes all dry mass.
Non‑numeric entries are coerced to zero and rejected.
Very large ratios reduce nitrogen to near zero and inflate the blend.
Rounding changes after unit toggles can shift displayed totals.
Clipboard access may be blocked by browser permissions.
File downloads can be blocked by popup settings.
JSON rendering escapes <, >, and & for safety.

Step‑by‑Step Guide:

Compost balance is computed from dry matter and ingredient ratios to guide a practical blend.

Choose your preferred unit system. Units
Set a lower and upper target band. 25 to 35
Decide whether to remove water from weights. Moisture
Add ingredients and check their ratios and moisture.
Enter weights, keeping units consistent across rows.
Review the blended ratio and classification.
If outside the band, adjust browns or greens and recalc.

Example: Leaves, kitchen scraps, and grass at the defaults land near 34 to 1 inside a 25 to 35 band.

Once the ratio sits inside your band, build and monitor moisture and turning cadence.

FAQ:

Is my data stored?

No. All computation and exports happen on your device; nothing is sent to a server.

Clipboard and downloads use standard browser APIs.

How accurate is the ratio?

Accuracy depends on realistic moisture estimates and representative ratios for your materials. If in doubt, recheck after a first turn and adjust inputs.

Which units are supported?

Kilograms and pounds are available. Switching units converts current entries and rounds to three decimals.

Can I work without a connection?

Yes. Calculations, copying, and downloads run locally. Some browsers restrict clipboard and downloads without user interaction.

How do I reach 30 to 1?

Lower numbers need more browns; higher numbers need more greens. Adjust a single ingredient at a time and recheck the blended ratio.

What does “borderline” mean?

Values near the band edges are sensitive to small changes in moisture or weights. Treat them as provisional and confirm after mixing.

Is there a cost or license?

No pricing or license terms are shown in the package files. Use within your organization’s policies.

Glossary:

Carbon to nitrogen ratio: Parts of carbon to one part nitrogen in dry matter.
Browns: Carbon‑rich, usually drier materials like leaves or straw.
Greens: Nitrogen‑rich, wetter materials like food scraps or grass.
Moisture: Percent water by weight before blending.
Dry mass: Material weight after removing water content.
Classification: Balanced, nitrogen heavy, or carbon heavy relative to the band.