Compost Calculator
Calculate how much brown (carbon-rich) and green (nitrogen-rich) material your compost bin or pile needs at a target brown-to-green ratio by volume.
cu ft
Total Volume
27.0 cu ft
Brown Material Needed
20.3 cu ft
Green Material Needed
6.8 cu ft
How Compost Material Ratios Are Calculated
A healthy compost pile needs the right balance of "brown" (carbon-rich) materials like dry leaves, straw, and cardboard, and "green" (nitrogen-rich) materials like food scraps, grass clippings, and coffee grounds. A common starting guideline is a 3:1 ratio of brown to green material by volume, though this is adjustable — some composters prefer a 2:1 ratio for faster breakdown. Enter your bin or pile's total volume (directly, or from length × width × height), plus your target ratio, to see how much of each material type to add.
Green Volume = Total Volume × [Green ÷ (Brown + Green)]
Example
A 27 cubic foot bin (3 × 3 × 3 ft) at a 3:1 brown-to-green ratio needs 20.25 cubic feet of brown material (dry leaves, cardboard) and 6.75 cubic feet of green material (food scraps, grass clippings) to fill it at the target ratio.
Common Use Cases
- Planning how much dry leaves or cardboard to stockpile alongside kitchen scraps.
- Balancing a compost pile that's too wet or smelly (usually too much green material).
- Sizing a new compost bin or pile before starting it.
FAQs
What counts as "brown" versus "green" material?
Browns are dry, carbon-rich materials — dried leaves, straw, shredded cardboard, and wood chips. Greens are moist, nitrogen-rich materials — food scraps, fresh grass clippings, and coffee grounds. Browns provide energy for decomposer microbes; greens provide the nitrogen they need to grow and reproduce.
What happens if the ratio is off?
Too much green material tends to make a pile wet, compacted, and smelly (excess nitrogen breaking down anaerobically). Too much brown material slows decomposition way down since there isn't enough nitrogen to fuel the microbes. The 3:1 or 2:1 brown-to-green guideline by volume helps avoid both.
Is this ratio by volume or by weight?
By volume — this is the more common and practical way home composters measure materials, since it's much easier to eyeball a bucket or wheelbarrow load than to weigh compost ingredients.