Compost Calculator
Built by Johnny Alto · free, no sign-up · updated July 26, 2026
A hot, fast compost pile needs the right balance of greens and browns. Enter how much green material you are adding to see how many parts of brown material to mix in, plus whether your pile is big enough to heat up. Balance is the difference between rich compost in weeks and a slimy or stalled heap.
Add about0cubic feet of browns
Total pile size0cubic feet
Greens are nitrogen-rich and wet: food scraps, fresh grass, coffee grounds, manure. Browns are carbon-rich and dry: dead leaves, straw, cardboard, sawdust. Roughly 2 to 3 parts browns to 1 part greens by volume gives a balanced pile; add more browns if it smells, more greens if it will not heat.
Getting the browns to greens ratio right
Composting is really about feeding microbes the right diet of carbon and nitrogen. Greens supply nitrogen and moisture, and browns supply carbon and structure. By volume, a ratio of roughly two to three parts browns for every one part greens keeps the pile balanced. Too many greens and the pile turns wet, smelly, and anaerobic; too many browns and it dries out and stalls.
This calculator takes the amount of green material you are adding and tells you how many parts of brown to layer in, along with the total pile size. Because greens vary in wetness, it lets you lean toward more browns for wet kitchen scraps or fewer for drier material.
Size matters for heat
A pile needs mass to insulate itself and hold the heat that microbes generate. About one cubic yard, a cube roughly three feet on each side, is the sweet spot where a pile can climb into the hot composting range and break material down in weeks rather than months. Smaller piles still compost, just more slowly and cooler, so build up to a good size before you expect fast results.
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Frequently asked questions
What is the ratio of browns to greens in compost?
By volume, aim for roughly 2 to 3 parts browns for every 1 part greens. Lean toward more browns if the pile is wet or smelly, and more greens if it will not heat up.
What counts as greens and browns?
Greens are nitrogen-rich and moist: food scraps, fresh grass clippings, coffee grounds, and manure. Browns are carbon-rich and dry: dead leaves, straw, cardboard, and sawdust.
How big does a compost pile need to be?
About one cubic yard, a cube around 3 feet on each side, is ideal. That mass lets the pile insulate itself and reach hot composting temperatures.
My compost smells bad, what do I do?
A sour or rotten smell usually means too many greens and not enough air. Mix in more browns, such as dry leaves or shredded cardboard, and turn the pile to add oxygen.
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