Compost Ratio Calculator
Balance green and brown weights, carbon-to-nitrogen ratios, manure, food scraps, pile moisture, aeration material, pile volume, and a custom target C:N ratio.
Load a real pile scenario, then adjust weights, moisture, manure, food scraps, aeration, and the target C:N ratio for your compost system.
Compost Mix Results
Your compost ratio results will appear here.
Grass, weeds, and garden trimmings feed microbes quickly but can mat down when added too thickly.
Leaves, straw, paper, and stalks absorb moisture and keep the pile from becoming sour.
Chicken, rabbit, sheep, cow, and horse manure pull high-carbon piles closer to hot-compost range.
Coarse chips, straw, stalks, leaves, and biochar create pore space for oxygen between turnings.
| Material | Typical C:N | Moisture estimate | Best compost use |
|---|---|---|---|
| Fresh grass clippings | 17:1 | 75% | Quick nitrogen; blend thinly with dry browns to prevent matting |
| Vegetable scraps | 15:1 | 85% | Wet kitchen greens; bury in the pile core with absorbent browns |
| Fruit scraps | 35:1 | 80% | Moderate carbon food waste; chop and cover well |
| Coffee grounds | 20:1 | 60% | Dense green material; scatter through leaves or straw |
| Alfalfa hay or pellets | 12:1 | 12% | Dry but nitrogen rich; useful for waking up a leaf pile |
| Green garden trimmings | 30:1 | 70% | Flexible middle material for steady microbial activity |
| Material | Typical C:N | Moisture estimate | Structure note |
|---|---|---|---|
| Dry autumn leaves | 60:1 | 15% | Reliable brown with good moisture absorption after shredding |
| Straw | 80:1 | 12% | Excellent airflow and moderate carbon correction |
| Shredded paper | 170:1 | 8% | Absorbent carbon; mix well so it does not clump |
| Shredded cardboard | 350:1 | 8% | Strong carbon correction for wet kitchen-heavy piles |
| Wood chips | 400:1 | 20% | Long-lasting aeration; slower to fully decompose |
| Sawdust | 500:1 | 10% | Powerful brown amendment; add in thin layers only |
| Manure type | Typical C:N | Moisture estimate | Compost handling note |
|---|---|---|---|
| Chicken manure | 10:1 | 65% | Very nitrogen rich; use modestly and cover with browns |
| Rabbit manure | 12:1 | 55% | Strong green boost with less water than poultry manure |
| Sheep manure | 16:1 | 60% | Balanced manure for warming a cool pile |
| Cow manure | 20:1 | 80% | Wet and moderate; needs dry browns for structure |
| Horse manure | 22:1 | 70% | Often mixed with bedding; check actual straw or shavings content |
| No manure | 0 | 0% | Use when food scraps or grass already provide enough nitrogen |
| Compost check | Low range | Good range | Action if outside range |
|---|---|---|---|
| C:N ratio | Below 25:1 | 25:1 to 35:1 | Add browns if low; add greens or manure if high |
| Moisture | Below 45% | 50% to 60% | Add water if dry; add browns and turn if wet |
| Active pile volume | Under 27 cu ft | 27 to 125 cu ft | Small piles cool faster; insulate or use a tumbler |
| Wet bulk density | Under 3 lb/cu ft | 5 to 12 lb/cu ft | Fluff dense piles; add volume to thin airy piles |
| Aeration score | Below 35 | 45 to 80 | Add coarse browns and turn before odors develop |
Moisture tip: If the pile drips when squeezed, mix in shredded cardboard, dry leaves, straw, or stalks before adding more wet food scraps.
Aeration tip: A pile can have the right C:N ratio and still stall if it is compacted. Coarse browns keep oxygen moving through the core.
To create a successful compost pile, people must provides the microbes in the compost pile with a proper balance of compost pile materials. A compost pile will not become successful if people just continuously add compost pile materials without a plans. Instead, a compost pile will become successful if the person understand how to balance the carbon and nitrogen within the compost pile.
If there is to many nitrogen within the compost pile, the compost pile will emit the smell of ammonia. Additionally, if there is to much carbon within the compost pile, the compost pile will break down very slow. By using a calculator that determine the carbon to nitrogen ratio in a compost pile, individuals can monitor the moisture within the compost pile as well.
Balancing Carbon and Nitrogen in Compost
Moisture are essential to creating a compost pile. The compost pile should feel wet like a wrung out sponge. People may add too much moisture when adding food scraps to the compost pile or adding grass clipping.
If the compost pile have too much moisture, dry brown materials can be added to the compost pile or the composting process can be continually turned to allow the moisture within the compost pile to evaporate. Aeration is another essential component of composting. Aeration provide oxygen to the center of the compost pile.
If there is not enough oxygen for the compost pile, the compost pile will become anaerobic and will produce bad smelling. Compost piles that contains coarse materials like wood chips or straw will allow for the creation of air pockets that provides oxygen to the center of the compost pile. Different compost pile materials will contain different amount of nitrogen and carbon to the compost pile.
For example, adding chicken manure will add a large amount of nitrogen to the compost pile, but it will also add moisture to the compost pile. Horse manure will also add nitrogen to the compost pile, but the bedding material added by the horses will change the carbon content and the structure of the compost pile. Not all brown materials are create equally, and not all green materials will provide the same benefit to the compost pile.
For example, sawdust is a brown material, but if added in excess, can slow the composting process. Shredded leaves will also provide brown material but will allow more airflow into the compost pile. Coffee grounds are a green material but are more dens than some may believe.
The carbon-to-nitrogen ratio calculator allow individuals to make better decisions regarding the compost pile materials they will add to the compost pile. Using the calculator, individuals can see the outcomes of various compostable materials. By using the calculator and understanding how the materials within a compost pile will interact with one another, humans can make adjustments to the compost pile itself.
Over time, individuals will learn the signals that tell them if they need to add cardboard or manure to there compost pile to maintain a consistent compost pile throughout the year.
