In our guide to the Carbon: Nitrogen ratio, we took an in-depth look at the role of the essential nutrients in composting.
As discussed there, you CAN compost with a wide range of C: N ratios.
Moreover, while you can calculate exact ratios, it’s complex, time-consuming and probably far more involved than the average home composter needs to worry about.
Sometimes even finding the C:N ratio of different materials can be challenging.
When you DO find them, sources can disagree, as you can tell from the table on manure below!
At the same time, if you are a keen composter, it is handy to have a rough idea of the C: N ratio of different materials.
So, using various sources, I’ve compiled a table showing the C: N ratios of common organic materials. I hope you find it useful!
Carbon: Nitrogen ratios for food waste
| Organic Material | C:N Ratio | Source |
| Cocoa shells | 22:1 | On-Farm Composting Handbook |
| Coffee Grounds | 20:1 | On-Farm Composting Handbook |
| Corn cobs | 56:1 -123:1 (Average: 98:1 | On-Farm Composting Handbook |
| Food waste | 14:1 -16:1 | On-Farm Composting Handbook |
| Fruit waste | 15:1 – 35:1 | Pavlis, Compost Science |
| Poultry carcasses | 5-1 | On-Farm Composting Handbook |
| Vegetable produce | 19:1 | On-Farm Composting Handbook |
| Vegetable waste | 11:1 to 13:1 | On-Farm Composting Handbook |
Carbon: Nitrogen ratios for grasses, straws and hays
| Organic Material | C:N Ratio | Source |
| Alfalfa | 18:1 | LibreTexts |
| Alfalfa pellets | 15:1 | Pavlis, Compost Science |
| General straw | 48:1-150:1Average: 80 | On-Farm Composting Handbook |
| Oat straw | 48:1-98:1 | On-Farm Composting Handbook |
| Wheat straw | 100:1-150:1 | On-Farm Composting Handbook |
| Legume hay | 15:1-19:1Average: 16 | On-Farm Composting Handbook |
| Rye grass | 30:1 | LibreTexts |
| Grass Clippings | 9:1-25:1 Average:17 | On-Farm Composting Handbook |
Carbon: Nitrogen ratios for woody materials
| Organic Material | C:N Ratio | Source |
| Paper from domestic use | 127-178 | On-Farm Composting Handbook |
| Fir bark | 540:1 | LibreTexts |
| Hardwood bark | 116:1 – 436:1 | On-Farm Composting Handbook |
| Softwood bark | 131:1-1,285:1 | On-Farm Composting Handbook |
| Redwood sawdust | 1020:1 | LibreTexts |
| Corrugated cardboard | 563:1 | On-Farm Composting Handbook |
| Sawdust | 200:1-750:1 | On-Farm Composting Handbook |
| Shrub trimmings | 53:1 | On-Farm Composting Handbook |
Carbon: Nitrogen ratios for manures
| Manure | C: N Ratio (Modern Farmer) | C: N Ratio Average (On Farm Handbook) |
| Cow | 25:1 | 19:1 |
| Horse | 20:1 | 30:1 |
| Humanure | 10:1 | 6:1 – 10:1 |
| Poultry | 7:1 | 6:1 (for laying hens) |
| Sheep | 15:1 | N/A |
| Swine | 12:1 | 14:1 |
| Turkey | N/A | 16:1 |
Carbon: Nitrogen ratios for other organic materials
| Organic Material | C:N Ratio | Source |
| Blood meal | 3:1 | Pavlis, Compost Science |
| Fresh weeds | 10:1 – 30:1 | Pavlis, Compost Science |
| Leaves | 40:1-80:1 | On-Farm Composting Handbook |
| Oak leaves | 26:1 | Compost Fundamentals |
| Peat moss | 58:1 | Compost Fundamentals |
| Pine needles | 60:1 to 110:1 | Compost Fundamentals |
| Seaweed | 5:1-27:1 | On-Farm Composting Handbook |
| Yard waste | 30:1 | Pavlis, Compost Science |
Wrapping up
Before finishing, I think it’s worth noting that ratios can vary from source to source.
What’s more, the final ratio can vary on many factors.
For example, if you are pulling weeds out, it might depend on how much soil is clinging to the roots.
If you are cleaning out animal droppings, it’s going to depend on the bedding material you use.
So while these are handy as a rough guide, it’s difficult to be exact when it comes to adding C: N ratios.
The key here is don’t worry too much – get it roughly right, and you’ll still get great compost.
Sources
On-Farm Composting Handbook Appendix A: Table A.1
LibreTexts: Carbon/Nitrogen Ratio
Washington State University: Compost Fundamentals
Modern Farmer: Get a Load of Our Manure Guide
Robert Pavlis, 2023, Compost Science for Gardeners
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