Built for active composters

Plan the pile, size the application, prove the payoff.

These free calculators help you balance greens and browns, fix pile moisture, size compost for a raised bed, plan lawn topdressing, and put a number on what your compost is worth — all built on research-backed formulas.

Browse all 10 calculators Inspect sources and formulas
Balance a new pile Blend your greens and browns before you build. Fill a raised bed Turn your bed's dimensions into compost volume and a bag count. Measure climate impact See what your landfill diversion is worth in CO2e.
Catalog size 10 tools

Covers pile building, amendment planning, and impact tracking.

Unit support US + metric

Every calculator works in both, and remembers your preference between visits.

Source base USDA + extension

Every threshold and formula traces back to a field guide, not forum lore.

Workflow Fast inputs

Built for quick decisions when you're standing in the yard, shed, or greenhouse.

Choose the job

Start from the problem you are solving.

Build and troubleshoot the pile

Head here when you need to balance feedstocks, fix moisture, or figure out whether the pile is heating the way it should.

 Figure out how much compost to apply

Head here when you're filling raised beds, topdressing a lawn, improving a garden bed, or mixing compost into containers.

 Quantify value, savings, and worm systems

Head here when you want to put a number on compost value, calculate carbon savings, or size a worm bin that can keep up with your scraps.

Mix and pile management

Balance your recipe, fix pile moisture, and track temperature before a slow, wet, or smelly pile turns into a bigger problem.

Most useful on day one

Amendment and application planning

Figure out how much compost a raised bed, lawn, garden bed, or container mix actually needs, so you buy the right amount and apply it at a safe depth.

Where most finished compost gets used

Value, impact, and indoor systems

Put a number on compost value, estimate carbon savings, and size a worm system when you need real figures for budgeting, reporting, or planning a setup.

Useful for reporting and planning
Why trust this

Science-backed compost calculators for piles, beds, lawns, and worm bins.

Use these tools to work out carbon-to-nitrogen ratio, moisture, raised bed volume, lawn topdressing depth, garden bed amendment rates, container mix percentages, compost value, and CO2 savings — without guessing.

The formulas trace back to sources you can check yourself: NRAES-54, USDA and EPA references, and extension programs from Cornell, Penn State, NC State, Oregon State, and other land-grant schools.

What gardeners need most
  • Fast compost ratio and moisture checks before the pile stalls.
  • Raised bed, lawn, and garden volume math that converts directly to bags or cubic yards.
  • Clear compost temperature, moisture, and application targets instead of vague advice.
Sources and formulas

If you want the formulas, ranges, and sources behind these numbers, see the full methodology and citation list.

All calculators pull from USDA data, university extension services, and the US Composting Council's CREF feedstock database. When sources disagree, we show you both values. See our full methodology and citations.
Common questions

Frequently Asked Questions

Quick answers to the thresholds and application rates people ask about most before they open a calculator.

What is the ideal carbon-to-nitrogen ratio for composting?

Aim for a starting C:N ratio of 25:1 to 35:1 — 30:1 is the number most extension services, including Cornell and NC State Extension, cite as optimal. Piles in that range decompose actively and heat up reliably. Go below 20:1 and excess nitrogen off-gasses as ammonia, causing odor and nutrient loss. Go above 40:1 and decomposition slows because the microbes run out of nitrogen. Use the C:N Ratio Calculator to blend "greens" (grass clippings, food scraps, manure) with "browns" (dry leaves, straw, cardboard) until you hit your target.

How hot should a compost pile get?

Active thermophilic composting sits around 131–160°F. The EPA's PFRP standard calls for temperatures above 131°F for several days straight to kill weed seeds and human pathogens. Push past 160°F and you can start killing off the beneficial microbes doing the work — turn the pile or add water to bring it back down. Below 105°F, the pile has dropped into the mesophilic phase: slower, but still going. The Pile Temperature Tracker tells you which phase you're in and what to do about it.

How do I know if my compost pile is too wet or too dry?

Try the squeeze test: grab a handful and squeeze firmly. At ideal moisture (50–60% by wet weight), it holds together and releases just a drop or two of water — like a wrung-out sponge. If water streams out freely, you're above 65% moisture and risking anaerobic conditions (and the odor that comes with them). If it crumbles apart without releasing any water, you're below 40% and decomposition has stalled. The Moisture Calculator walks you through the squeeze test, gives you an oven-dry calculator for a precise reading, and tells you how much water to add to a dry pile.

How much compost does a raised bed need?

For a new raised bed, 30–50% compost blended with topsoil and other amendments is typical. For an annual top-dress on an established bed, most extension services recommend working 1–2 inches of compost into the top 6 inches of soil. For soil remediation in compacted or poor soil, you can go up to 4 inches incorporated 8–12 inches deep. Enter your bed dimensions into the Raised Bed Calculator and it'll give you cubic feet, cubic yards, liters and how many bags to buy.

What is the carbon-to-nitrogen ratio of common composting materials?

C:N ratios vary a lot by material. High-nitrogen "greens": fresh grass clippings (15–20:1), vegetable scraps (12–20:1), coffee grounds (20:1), chicken manure (7–15:1), blood meal (3:1). High-carbon "browns": dry autumn leaves (40–80:1), straw (75–100:1), cardboard (200–500:1), wood chips (200–750:1), sawdust (200–750:1). A balanced pile typically runs a 3:1 volume ratio of browns to greens, though the exact number depends on what you're actually using. The C:N Ratio Calculator pulls per-material density and moisture data from NRAES-54 and CREF, so results stay accurate across 45+ feedstocks.

How much compost should I apply to a lawn?

Penn State Extension recommends ¼ to ½ inch of finished compost for routine topdressing, spread and raked in to fill the thatch. Go over ½ inch, especially in one application, and you risk smothering the grass. For overseeding, ¼ inch gives you a seedbed without burying the seed. Damaged or patchy areas can handle up to ½ inch. The Lawn Topdressing Calculator works out cubic yards and bags for any area, walks you through seasonal timing by grass type, and flags it if you enter a depth past the safe threshold.

Is home compost worth anything financially?

Yes. A cubic yard of finished compost retails for $35–80 depending on location and type. Beyond what it would cost to buy, compost delivers plant-available nitrogen, phosphorus, and potassium. Using Oregon State University's PAN guidance, the first-year plant-available nitrogen in a typical mature compost (1–1.5% total N, 10–20% first-year availability) works out to $0.50–1.50 per cubic foot in fertilizer savings alone. The Compost Value Calculator works out retail value, fertilizer value, and combined savings for your specific volume.