from the employee owners at Gardener's Supply Co.

How Much Soil Do I Need?

Raised beds

3 x 6 ft. beds, such as these Copper Cap Raised Beds, hold 15 cubic feet of soil.

Good soil is the single most important ingredient for a good garden. Raised beds give you an immediate advantage over a regular garden, because when you fill your raised bed, you can fill it with a blend of soil that’s superior to the native soil in your yard. Soil that’s loose and rich with nutrients and organic matter will allow the roots of your plants to grow freely, and ensure that they have access to the water and nutrients they need to sustain healthy growth.

Example: How Much Soil Do I Need for a 3×6 Bed?

To fill a 3×6 bed with 10″ sides, you will need 15 cubic feed of blended soil. To create the blend, use the following quantities:

  • 9 cubic feet of topsoil (9 20-quart bags)
  • 4.5 cubic feed of compost (4.5 20-quart bags)
  • 1.5 cubic feet of soilless growing mix
  • 1.5 cups Gardener’s Supply All-Purpose Fertilizer

Here’s how:

  1. Measure your raised bed and calculate the amount of soil you need to fill it. Not so good with math? Use our Soil Calculator.
  2. Use The Recipe, below, to create the right blend.

‘The Recipe’

If you’ll be filling more than one raised bed, you may want to buy your soil in bulk — by the cubic foot or cubic yard. We recommend these proportions:

  • 60% topsoil
  • 30% compost
  • 10% soilless growing mix that contains peat moss, perlite and/or vermiculite, such as ProMix

Keep in mind that proportions are approximate because soil volume varies from source to source. For instance, if the Soil Calculator specifies 0.444 cubic yards of soil for your bed, go ahead and round it up to a half yard.

If you do not have access to quality topsoil, an acceptable substitute would be a 50-50 blend of soilless growing medium and compost. If you want to add peat moss to the bed, it should not be more than 20 percent of the total mix. Peat moss is naturally acidic and is not a good medium for growing vegetables.

3 Comments

  1. March 28, 2011    

    What is the negative impact of using a higher portion of compost, even 100% compost?

  2. March 28, 2011    

    In short, too much of a good thing. Pure compost does not provide good soil structure for optimum root growth and drainage.

    Keep in mind that the “recipe” is meant as a guideline, and you should feel free to experiment and adjust. Compost varies quite a bit, depending on how it’s made.

    -David Grist, Gardener’s Supply

  3. November 5, 2012    

    In addition to the helpful soil calculator provided, some readers might want to have a ballpark price for topsoil. The price for topsoil in Dallas TX
    is about $115.00 – $295.00 per load (10 cubic yds) depending upon how far it needs to be taken for delivery. There are different grades of topsoil too.

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We are an employee-owned company of avid gardeners, located in Burlington, VT.