Compost Ratio Calculator

Balance browns and greens in your compost.

Browns (carbon-rich)

parts

Greens (nitrogen-rich)

parts

Results update as you type.

Browns : greens ratio

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Recommended browns (3:1)—

Balance—

How it works

Successful composting depends on balancing carbon-rich browns with nitrogen-rich greens, and this calculator helps you get the mix right. You enter the amounts of browns and greens you have, and it returns the browns-to-greens ratio, the recommended browns amount for a good mix, and an assessment of your balance. Browns are dry, carbon-rich materials like dead leaves, straw, cardboard, and wood chips, while greens are moist, nitrogen-rich materials like grass clippings, vegetable scraps, and coffee grounds. Microbes need both carbon for energy and nitrogen for protein to break down the pile efficiently. By volume, a ratio of roughly two to three parts browns to one part greens works well for most home compost, keeping the pile aerated and preventing problems. Too many greens make the pile wet, dense, and smelly, as excess nitrogen and moisture lead to anaerobic conditions and odor, while too many browns make it dry and slow, since the microbes lack the nitrogen to work quickly. The calculator flags which situation you are in and suggests adding browns or greens to correct it. Note that this uses a practical volume-based ratio, which differs from the scientific carbon-to-nitrogen mass ratio of around 25 to 30 to 1 that soil scientists cite; the volume rule of thumb is easier for everyday composting. Keep the pile moist like a wrung-out sponge and turn it for air. Enter your browns and greens to check the ratio.

Formula

Ratio = browns / greens (aim for about 2:1 to 3:1 by volume)

Good compost needs a balance of carbon-rich browns and nitrogen-rich greens. By volume, a browns-to-greens ratio of roughly 2:1 to 3:1 is ideal. The calculator divides your browns by greens to find the ratio and recommends the browns amount for a 3:1 mix based on your greens.

Source:Composting guidelines

We review all our tools from time to time to ensure accuracy.

Worked example

Browns (carbon-rich):3Greens (nitrogen-rich):1

3 parts browns to 1 part greens is 3:1 — well balanced.

How to use this calculator

1
Enter your values
Enter browns (carbon-rich) and greens (nitrogen-rich).
2
Adjust the options
Fine-tune any options to match your situation.
3
Read your result
Browns : greens ratio updates instantly as you type — no button to press.

Frequently asked questions

What is the ideal compost ratio?

By volume, a browns-to-greens ratio of roughly 2:1 to 3:1 works well for most home compost. This balances the carbon-rich browns that provide energy and structure with the nitrogen-rich greens that fuel microbial activity. The calculator checks your ratio against this range and tells you whether to add more browns or greens.

What are browns and greens in composting?

Browns are dry, carbon-rich materials such as dead leaves, straw, cardboard, paper, and wood chips. Greens are moist, nitrogen-rich materials like grass clippings, fruit and vegetable scraps, and coffee grounds. A compost pile needs both: carbon for energy and structure, and nitrogen for the proteins microbes need to break everything down.

What happens if I have too many greens?

Too many greens make the pile wet, dense, and smelly. Excess nitrogen and moisture create anaerobic conditions where the wrong microbes thrive, producing foul odors and slimy, matted material instead of good compost. Adding more browns restores airflow and balance, absorbing excess moisture and giving the pile structure to decompose properly.

What happens if I have too many browns?

Too many browns make the pile dry and slow to decompose. With too little nitrogen, the microbes lack the fuel to work quickly, so the pile just sits without breaking down. Adding greens, or a little water and a nitrogen source, kick-starts activity. A balanced ratio keeps decomposition steady and efficient.

How does this differ from the carbon-to-nitrogen ratio?

Soil scientists cite an ideal carbon-to-nitrogen mass ratio of about 25 to 30 to 1 for compost. That is a chemical measure by weight, whereas this calculator uses a simpler volume-based browns-to-greens ratio of about 2:1 to 3:1, which is far more practical for home composters estimating by the bucketful. Both aim at the same balanced result.