Browns and greens: the reference list
Almost every compost problem — smell, sogginess, a heap that won’t start — traces back to the balance between two broad categories of material: browns and greens. This page is a quick reference for what falls into each, and roughly how much of each to use.
Quick fix
- Browns are dry and carbon-rich: cardboard, dry leaves, straw, paper.
- Greens are moist and nitrogen-rich: kitchen scraps, grass clippings, fresh weeds.
- Aim for roughly two to three parts browns to one part greens by volume, not by weight.
The reference list
| Browns (carbon) | Greens (nitrogen) |
|---|---|
| Cardboard, torn or shredded | Kitchen scraps (fruit, veg, peelings) |
| Dry leaves | Coffee grounds and tea leaves |
| Straw | Grass clippings |
| Plain paper, shredded | Fresh weeds (not gone to seed) |
| Wood chips | Manure from herbivores (horse, chicken, rabbit) |
| Sawdust (from untreated wood only) |
Browns tend to be dry, tan or grey in colour, and slow to break down on their own. Greens tend to be moist, green or brightly coloured, and quick to break down — often too quick, which is part of why they need browns to balance them.
Why “browns” and “greens” are useful shorthand
The actual property that matters is the ratio of carbon to nitrogen in the material, but almost nobody measures that directly at home, and you don’t need to. Dry, woody, fibrous material is reliably high in carbon; fresh, moist, recently-alive material is reliably high in nitrogen. The colour-based shorthand of browns and greens tracks that underlying chemistry closely enough to be genuinely useful without needing a lab test.
The rough ratio
A commonly cited starting point is two to three parts browns to one part greens, measured by volume (a bucket of one to a bucket of the other), not by weight — greens are heavier for their volume, so weighing them would throw the ratio off. This isn’t a precise formula, and you shouldn’t treat it as one. It’s a starting ratio to correct toward, not a rule to measure out with scales. If your heap smells of ammonia or feels slimy and wet, you need more browns relative to what you’ve got. If it’s bone dry and nothing is happening, you may have gone too far the other way, or you simply need to add water alongside more greens.
Why ratio is a guide, not a rule
Different materials within each category vary a fair amount. Fresh grass clippings are wetter and more nitrogen-heavy than a fresh weed pulled from dry soil; cardboard holds its structure differently to dry leaves, which pack down more. Because of that, two heaps built to roughly the same “ratio” by two different people, using different materials, can behave quite differently. Treat the 2:1–3:1 figure as a sensible place to start, then adjust based on what you actually observe: smell, moisture, and how fast the pile is shrinking are all better feedback than trying to hit an exact number.
It’s also worth knowing that a heap doesn’t need a perfect ratio to work at all — it just needs to be in the right general range. Most of the guides on this site for specific problems (smell, sogginess, a stalled pile) come back to nudging this balance one way or the other, because it’s the single biggest lever you have over how a home compost heap behaves.
A practical habit
Many people find it easiest to keep a stash of browns — a bag of dry leaves, a stack of flattened cardboard — sitting near the compost heap, so that every time you add a bucket of kitchen scraps, you can immediately mix in a roughly matching handful or two of browns without having to go find some. That single habit prevents more compost problems than almost anything else on this site.