Compost Calculator
Mix browns (carbon-rich) and greens (nitrogen-rich) materials and check whether your combination lands in the ideal carbon-to-nitrogen ratio for fast, odor-free composting.
What this calculator does
The Compost Calculator estimates the overall carbon-to-nitrogen (C:N) ratio of a compost pile based on the volumes of “brown” (carbon-rich) and “green” (nitrogen-rich) materials you plan to combine, and compares it against the ideal range for active, odor-free composting.
The formula it uses
Each material type has a typical published C:N ratio (for example, dry leaves are roughly 60:1, while grass clippings are roughly 20:1). This calculator takes a volume-weighted average of the materials you enter: Mix C:N = (Brown Volume × Brown C:N + Green Volume × Green C:N) / Total Volume. The ideal target for active composting is generally cited as around 25:1 to 35:1.
It also estimates finished compost volume, since a pile typically shrinks by roughly half to two-thirds as materials break down and settle.
A note on accuracy
Published C:N ratios for a given material vary depending on moisture, age, and source, so treat these numbers as a general planning guide rather than a lab-verified measurement. Aim for the target range, and adjust by adding more browns if the pile smells or feels too wet, or more greens if it isn’t heating up.