Data · Source-cited · 32 materials
Compost C:N Ratios by Material
A reference table for common compost greens, browns, and neutral materials. Use it to understand why grass clippings heat a pile quickly, why sawdust slows one down, and how to balance a home compost mix before it smells or stalls.
Target pile range: 25:1-30:1·6 extension sources·CSV-ready table
Method
- Ratios are typical ranges, not lab guarantees. Moisture, age, bedding, and particle size can shift a material substantially.
- Greens are nitrogen-rich inputs that usually heat or activate a pile. Browns are carbon-rich inputs that add structure and reduce odor.
- The practical starting target for an active home pile is around 25:1 to 30:1. Use the table as a planning reference, then adjust by smell, moisture, and pile temperature.
Material C:N ratio table
Download CSV| Material | Type | Typical C:N ratio | Moisture note | Best use | Source |
|---|---|---|---|---|---|
| Grass clippings | Green | 9-25:1 | Wet and compacting | Mix thinly with dry leaves or straw | Cornell-CWMI |
| Vegetable scraps | Green | 12-20:1 | Moist | Bury inside pile to reduce pests | CSU-Compost |
| Fruit scraps | Green | 20-35:1 | Moist and sugary | Mix with browns, avoid exposed layers | UMN-Home |
| Coffee grounds | Green | 20:1 | Moist and dense | Blend with leaves, not as a thick mat | Cornell-CWMI |
| Tea leaves | Green | 25:1 | Moist | Small nitrogen boost in kitchen-scrap layer | OSU-Ask |
| Fresh garden weeds | Green | 20-30:1 | Moist | Use before seed set; mix with browns | UIUC-Trouble |
| Fresh legume hay | Green | 12-25:1 | Moist to semi-dry | Nitrogen-rich layer for slow piles | Cornell-CWMI |
| Fresh poultry manure | Green | 6-15:1 | Wet and strong | Use sparingly; hot compost only | Cornell-CWMI |
| Fresh horse manure | Green | 22-50:1 | Moist with bedding | Good activator if bedding is not excessive | Cornell-CWMI |
| Fresh cow manure | Green | 18-25:1 | Wet | Blend well and compost before garden use | Cornell-CWMI |
| Alfalfa meal | Green | 12-15:1 | Dry | Small activator dose for carbon-heavy piles | Cornell-CWMI |
| Blood meal | Green | 3-5:1 | Dry | Very small activator dose only | CSU-Compost |
| Dry leaves | Brown | 40-80:1 | Dry and fluffy | Main brown material for kitchen scraps | Cornell-CWMI |
| Fresh leaves | Neutral | 30-45:1 | Moist | Good bulk material, shred if possible | Cornell-CWMI |
| Straw | Brown | 48-150:1 | Dry and airy | Add structure and oxygen channels | Cornell-CWMI |
| Hay | Brown | 15-32:1 | Variable | Use seed-free hay; mix evenly | Cornell-CWMI |
| Corn stalks | Brown | 60-75:1 | Dry and coarse | Chop before adding | Cornell-CWMI |
| Wood chips | Brown | 100-500:1 | Dry and slow | Use as structure, not main feedstock | CSU-Compost |
| Sawdust | Brown | 200-750:1 | Dry and compacting | Use thinly; mix with wet greens | Cornell-CWMI |
| Wood shavings | Brown | 100-400:1 | Dry | Useful for manure-heavy piles | Cornell-CWMI |
| Shredded newspaper | Brown | 150-200:1 | Dry | Shred and wet before adding | UMN-Home |
| Corrugated cardboard | Brown | 350-563:1 | Dry | Shred; pair with grass or food scraps | Cornell-CWMI |
| Paper towels | Brown | 110-160:1 | Variable | Only if not oily or chemical-soaked | UMN-Home |
| Pine needles | Brown | 60-110:1 | Dry and waxy | Use modestly; slow to break down | OSU-Ask |
| Bark mulch | Brown | 100-130:1 | Dry and coarse | Slow bulking material, better as mulch | CSU-Compost |
| Peanut shells | Brown | 35-60:1 | Dry | Crush or mix into active pile | Cornell-CWMI |
| Rice hulls | Brown | 70-120:1 | Dry and airy | Adds structure to wet piles | Cornell-CWMI |
| Spent potting mix | Neutral | 30-50:1 | Variable | Small amounts for bulk, not nutrition | UIUC-Trouble |
| Finished compost | Neutral | 10-20:1 | Moist and stable | Use as inoculant or curing material | UIUC-Questions |
| Garden soil | Neutral | Not feedstock | Variable | Small inoculant dose only; avoid heavy layers | CSU-Compost |
| Eggshells | Neutral | Not meaningful | Dry | Mineral addition; crush before adding | UMN-Home |
| Wood ash | Neutral | Not feedstock | Dry and alkaline | Avoid or use very sparingly | OSU-Ask |
How to cite this table
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APA
gardencalcs.com. (2026). Compost C:N ratios by material. Retrieved from https://gardencalcs.com/data/compost-cn-ratios
Chicago
gardencalcs.com. "Compost C:N Ratios by Material." Accessed 2026. https://gardencalcs.com/data/compost-cn-ratios.
Use it with the calculator
The table explains material behavior. The calculator turns your bin size and ingredient mix into a practical balancing recommendation.
Open compost calculatorSources
- Appendix A: Carbon/Nitrogen Ratios of Common Organic MaterialsCornell Waste Management Institute · cited as Cornell-CWMI
- Making CompostColorado State University Extension · cited as CSU-Compost
- Troubleshooting Composting ProblemsUniversity of Illinois Extension · cited as UIUC-Trouble
- Questions About CompostingUniversity of Illinois Extension · cited as UIUC-Questions
- Composting in Home GardensUniversity of Minnesota Extension · cited as UMN-Home
- Composting: Should I Turn, Cover, or Both?Oregon State University Extension · cited as OSU-Ask