Compost Calculator
Size a compost bin and balance the mix. Enter the bin size and how full it is, and see how much brown material, green material and finished compost you can expect.
| Detail | Result |
|---|---|
| Bin volume | 1 cu yd |
| Material in the bin | 24.3 cu ft |
| Finished compost (about) | 12.2 cu ft |
| 1 cu ft bags of compost | 13 |
See more of Backyard Calculators on Google
Add us as a preferred source to see our calculators and guides more often in Google Top Stories.
Was this calculator helpful?
How Compost Calculator Works
Four quick steps happen behind the screen every time you change a number.
Finds the bin volume
Length, width and height multiply to give the space inside your bin.
Applies the fill level
Only part of the bin holds material, because piles need air to work.
Splits browns and greens
The material is divided using the ratio you choose, such as two browns to one green.
Estimates the yield
Compost shrinks as it breaks down, so about half the volume remains when it is finished.
How to Use Compost Calculator
Five quick steps take you from a tape measure to a usable result.
- Measure the binEnter the inside length, width and height of your bin or pile area.
- Set how full it isFilling to 90 percent leaves space on top for mixing.
- Pick the ratioTwo parts browns to one part greens is a good start for most piles.
- Collect browns and greensBrowns are dry leaves, straw and cardboard. Greens are kitchen scraps and grass clippings.
- Plan the finished compostUse the yield to decide how many beds the compost will cover.
Formula Used in Compost Calculator
These are the standard formulas behind every result, so you can check the numbers yourself.
Bin volume
All sides are in feet, so V is in cubic feet.
Greens
Ratio is the number of browns for each green.
Browns
Browns make up the rest of the material.
Worked example
A 3 ft cube bin holds 27 cubic feet. Filled to 90 percent it holds 24.3 cubic feet. At two browns to one green that is 16.2 cubic feet of browns and 8.1 of greens, and about 12.2 cubic feet of finished compost.
Compost Bin Size Chart
Bin volume, browns, greens and finished compost for common bin sizes at 90 percent full and a 2 to 1 ratio.
| Size | Bin, cu ft | Browns | Greens | Finished |
|---|---|---|---|---|
| 2 × 2 × 2 ft | 8 | 4.8 | 2.4 | 3.6 |
| 3 × 3 × 3 ft | 27 | 16.2 | 8.1 | 12.2 |
| 3 × 4 × 3 ft | 36 | 21.6 | 10.8 | 16.2 |
| 4 × 4 × 4 ft | 64 | 38.4 | 19.2 | 28.8 |
| 5 × 5 × 4 ft | 100 | 60 | 30 | 45 |
| 6 × 4 × 4 ft | 96 | 57.6 | 28.8 | 43.2 |
A compost pile works best at 3 feet or larger on each side.
Browns and Greens Guide
Common materials and how to count them in the mix.
| Type | Examples | Role |
|---|---|---|
| Browns | Dry leaves, straw, cardboard, wood chips | Carbon and airflow |
| Greens | Kitchen scraps, grass clippings, plant trimmings | Nitrogen and moisture |
| Avoid | Meat, dairy, pet waste, oily food | Smell and pests |
Chop large pieces so they break down faster.
Common Compost Mistakes
Four slips that throw off the result, and how to avoid them.
Too many greens
Wet, smelly piles have too much nitrogen. Add dry browns and mix well.
Making the bin too small
Piles under a few feet across do not hold heat. Aim for at least three feet on each side.
Packing the pile tight
Compost needs air. Fill the bin loosely and turn it regularly.
Adding meat or dairy
These attract pests and cause odour. Keep to plant based scraps.
Tools You Must Know
One number is rarely enough for a yard project. These calculators pair well with this one.
Compost Calculator FAQs
Quick answers before you order materials.
How big should a compost bin be?
Three feet in each direction is a good size. It holds enough material to heat up and break down.
What is the right browns to greens ratio?
Start with two parts browns to one part greens by volume, and adjust if the pile smells or stays dry.
How much finished compost will I get?
Expect roughly half the volume you put in, as the material shrinks while it breaks down.
What counts as browns?
Dry leaves, straw, shredded cardboard and wood chips are browns. They add carbon.
What counts as greens?
Kitchen scraps, grass clippings and fresh plant trimmings are greens. They add nitrogen.
Is the Compost Calculator free?
Yes. It is free to use, with feet or metres and no signup.
Browse Our Categories
Explore every calculator by project type, from decks and fences to pools and gardens.