About compost.tools

What This Is

compost.tools is 10 free calculators built to help you make better composting and soil amendment decisions. Every one of them is grounded in research from USDA, university cooperative extension services, and the US Composting Council Research & Education Foundation's CREF feedstock database — the same sources the professionals use.

compost.tools started from a plain frustration: almost every basic composting decision — how much compost to add to a raised bed, whether a pile's C:N ratio is in range — means digging through scattered PDF extension guides and doing the arithmetic yourself. These calculators do that math for you, drawing on the same published sources, so you can spend your time on the pile.

Data Philosophy

Every number in every calculator traces back to a source you can check yourself. We rank those sources by a strict hierarchy:

• University cooperative extension publications — peer-reviewed, regularly updated, written for practical use
• USDA and EPA datasets — NRCS NEH Part 637, EPA WARM model
• On-Farm Composting Handbook (NRAES-54) — the field standard since 1992
• CREF Appendix B — the US Composting Council's regularly-updated feedstock database

When authoritative sources disagree — and it happens more than you'd think — we show both values and explain which one we picked and why. We don't just quietly go with whichever number sounds right. See the full methodology and citations page for every source and a table of known disagreements.

Transparency on Limitations

Composting runs on living systems, not equations. The C:N ratios in our feedstock database are representative ranges, not fixed constants — the same grass clippings can run anywhere from 9:1 to 25:1 depending on fertilization history, growth stage, and moisture. Our calculators get you a defensible starting point. They're not a guarantee.

If you're running a commercial or regulated composting operation, get a laboratory analysis of your feedstocks from a certified soil lab — we'd strongly recommend it. University extension services in every state offer subsidized testing.

Units

All calculators handle both US customary and metric units. Your preference gets saved in your browser's local storage, so it's still set the next time you visit. First-time visitors outside the US, Liberia, and Myanmar default to metric based on browser locale.

Who Writes This

The research, feedstock data, and calculator methodology are all written by Wes Calloway, a research writer. We're upfront about what that means: what you're getting here is careful sourcing and clear explanation, not a professional credential. Every figure traces to a citable publication, so you can check the work yourself. Read more about who writes compost.tools and our editorial standards.

No Account Required

compost.tools doesn't require registration, a login, or an email address. Every calculation runs right in your browser — none of your inputs get sent to our servers.

Advertising

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