Compost Calculator {Automatically Calculate Compost Volumes}

Trying to figure out your exact compost needs in terms of volume can be challenging and confusing — just use this simple, automatic compost calculator instead and let it do the work for you.

This compost calculator is both USA-based and metric to make it easier. Just select which version you want by easily toggling back and forth.

And it will automatically provide you with a wide variety of outputs: cubic feet, yards, meters, and liters too.

Simply enter the width and length of the area where you are applying compost, specify the depth of the compost, and that’s it.

If you’re not applying compost over the entire bed, simply select half the amount.

People typically apply anywhere from 1/2 inch of compost to 1 inch to maintain their garden beds to 6-inches if starting brand new no-till garden beds where they will be planting entirely in compost itself.

(And check out my mulch calculator for more handy gardening tools.)

Compost Calculator

(This will calculate the volume of compost in cubic feet, cubic yards, cubic meters, and liters).

US Units
Metric Units

You will need:

Compost volume in cubic feet:
0.00 ft3
Compost volume in cubic meters:
0.00 m3
Compost volume in cubic yards:
0.00 yd3
Compost volume in liters:
0.00 L

How Do You Calculate Compost Volume?

First, measure the area you are applying compost to.

In raised bed gardens this is very simple. But don’t worry if your numbers are only approximate due to irregular landscape shapes — it’s not that big of a deal.

And if you’re not applying compost to the entire entire, you can cut the amount in half.

My raised beds are 5 feet by 5 feet for example.

Next, you’ll need to add the depth of compost you are applying.

I prefer to add 1-inch of compost as mulch over the entire surface of the bed to slowly feed my soil and plants through the season.

The volume of compost you require is the result of those three things multiplied together: the width, the length and the depth.

Make sure you are using the same unit of measurement or your results will not work.

What that means is that you have to convert the depth you want to feet (assuming you’re working in feet for the width and length.)

Multiplying feet by inches doesn’t work. You have to multiply feet by feet or inches by inches. 

The formula to convert inches to feet is: multiply by 0.0833 and if you’re applying 1 inch, that means your third number is simply 0.0833 as demonstrated below.

Volume = width x length x depth

So 5 feet x 5 feet x 0.0833 = 2.08 ft3, 0.08 yd3, or 58.97 L

Just use the compost calculator above instead — it’s easier.

Compost FAQ

How Do I Work Out How Much Compost I Need?

How much compost you need depends on what type of gardening you do.

If you’re applying compost as mulch over the entire surface of your vegetable and garden beds, it is best to apply 1-inch of compost but you can get away with 1/2 an inch in fertile soils.

If you’re amending poor soil and will be tilling in the compost — up to 30% of the volume of the raised beds is a healthy amount, although people will use less and more sussefully.

If you’re planning a no-dig/no-till garden and you’re planting in 100% compost then you will need 6-inches of compost in your raised beds or ground to make that a success.

Check out my articles on soil vs compost and the best compost for raised beds for more information.

How Much Does 1 Cubic Yard Of Compost Cover?

One cubic yard of compost will cover 324 square feet of your garden surface or raised beds with 1-inch of compost.

How Much Does a 40 lbs Bag of Compost cover?

A typical 40-pound bag of compost covers 0.75 cubic feet of garden space.

Can I Just Put Compost On Top Of Soil?

You can put compost on top of soil as a mulch layer. If amending poor soils, you will get a better and faster benefit by digging it into the soils first and then applying it on top every season afterwards. If starting a no-dig/no-till garden with only compost, you need 6-inches of compost and it can be applied on top of soil

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Final Thoughts

Hopefully this compost calculator took some of the confusion and frustration in calculating compost needs away from your garden planning and maintenance.

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