Raised Bed Soil Calculator

Enter the size of the raised bed and its fill depth and get the soil as bags or bulk yards, split by a published mix into its own lines, each rounded up once.

Estimates for planning, not professional advice. Read the full notice.

Bed size

Feet and inches, like 12' 6"

Feet and inches, like 12' 6"

The depth of soil in the bed.

Example: a four by eight foot raised bed

1 yd³ to order (0.83 yd³ exact)

  • Bed volume 32 ft³
  • Bed volume in cubic yards 1.19 yd³
  • Bags of the size above for the whole bed 22 × 1.5 ft³ bags
  • Topsoil, cubic yards 0.83 yd³
  • Topsoil at the supplier's step 1 yd³

Shopping list

Example: a four by eight foot raised bed
ItemSizeBuy
Topsoil by the cubic yard1 yd³1 yd³
Compost by the cubic yard1 yd³0.5 yd³

Share this project

This link carries:

    The project is inside the link, after the # sign. Browsers do not send that part to the site.

    Worked example: a four by eight foot raised bed

    Show the working
    1. Area 8 ft × 4 ft = 32 ft²
    2. Bed volume at the fill depth 32 ft² × 1 ft = 32 ft³
    3. Split the volume by the mix, exactly 32 ft³ × 70 % topsoil = 22.4 ft³
    4. Compost is the rest of the mix 32 ft³ × 30 % compost = 9.6 ft³
    5. Round each line up once, to the supplier's yard step 0.83 yd³ = 1 yd³

    Assumptions

    The figures behind the example. Sourced figures link to their source below; a default is a starting value to check against your label or supplier.

    Landscape waste or overage 0%
    Default No silent overage. Check your label or supplier.
    Raised bed settling top-up 0%
    Default Bought as its own item, never folded into the fill. Check your label or supplier.
    Supplier's smallest yard step 0.5 yd³
    Default Suppliers sell bulk in steps. Check your label or supplier.
    Raised bed soil bag size 1.5 ft³
    Default Bag sizes are on the label. Check your label or supplier.
    Iowa State: topsoil share 70%[1]
    Iowa State Extension: equal parts topsoil, organic matter and coarse sand, or about 70% topsoil and about 30% compost.
    Maryland: topsoil in beds at least this deep 16 in[2]
    University of Maryland Extension: compost and purchased topsoil 1:2 or 1:1; or compost and a soilless mix 1:1; topsoil up to 20% by volume in beds at least 16 in deep.
    Clemson: compost share, lowest 10%[3]
    Clemson Extension: compost in a range of 10 to 20 percent of the total volume (length x width x height) of medium added to the bed.
    Mississippi State: minimum bed depth 6 in[4]
    Mississippi State Extension: 6 in is the recommended minimum depth of a raised bed.

    Bags or bulk for several beds

    Bulk yards and whole bags of topsoil and compost for one to six four by eight foot beds at a twelve inch fill, by bag size

    BedsBulk, cubic yards orderedBags of 1 ft³, both linesBags of 1.5 ft³, both linesBags of 2 ft³, both lines
    1 1.5 yd³33 bags22 bags17 bags
    2 3 yd³65 bags43 bags33 bags
    3 4 yd³97 bags65 bags49 bags
    4 5 yd³129 bags86 bags65 bags
    5 6.5 yd³160 bags107 bags80 bags
    6 7.5 yd³193 bags129 bags97 bags

    Each line is rounded up on its own, so the bag counts add the topsoil bags and the compost bags. The mix is the Iowa State topsoil and compost recipe.

    Questions

    How many bags of soil for a four by eight raised bed?

    The table counts whole bags for one to six beds at three bag sizes, with the topsoil and compost lines rounded up separately. Choose Bags in Buy as and pick your bag size for your own bed.

    How many cubic feet does a raised bed hold?

    The bed volume is length times width times the fill depth. The worked example shows it for a four by eight foot bed in cubic feet and in cubic yards.

    Why is settling a separate line?

    Fill settles, and a top-up for it is bought later, so the calculator keeps it as its own line, with a percent you set in the assumptions, instead of folding it into the fill. It starts at none.

    Sources (7)
    1. What would be a good soil mix for a raised bed? (Yard and Garden FAQ), Iowa State University Extension and Outreach, updated April 20, 2026. Code or government
      “An excellent soil mix can be prepared by mixing equal parts topsoil, organic matter (well-rotted manure, compost, or peat), and coarse sand. Another option is ~70% topsoil and ~30% compost.”
      Checked November 12, 2026. Figures and codes change; verify with the source. Back to where this is used
    2. Soil to Fill Raised Beds, University of Maryland Extension (J. Traunfeld), updated November 6, 2024. Code or government
      “Add a mixture of compost and purchased topsoil in a 1:2 or 1:1 ratio, to the top of the bed. ... Alternatively, fill the bed with compost and a soilless growing mix in a 1:1 ratio.”
      “Topsoil can be added (up to 20% by volume) for beds that are at least 16 inches deep.”
      “The organic matter (OM) content in a raised bed containing garden soil, should be 25%-50% by volume or 5%-15% by weight (as measured by a soil testing lab).”
      “Raised bed gardens placed on hard surfaces are fine if they are a minimum of 8 inches deep for leafy greens, beans, and cucumbers, and 12-24 inches deep for pepper, tomato, and squash.”
      Checked November 12, 2026. Figures and codes change; verify with the source. Back to where this is used
    3. Raised Beds (HGIC 1257), Clemson Cooperative Extension, Home and Garden Information Center, revised Aug 1, 2017. Code or government
      “The amount of compost added should be in a range of 10-20% of the total volume (length x width x height) of medium added to the bed.”
      Checked November 12, 2026. Figures and codes change; verify with the source. Back to where this is used
    4. Constructing Raised Beds for the Mississippi Gardener (P3087), Mississippi State University Extension, web page, no date shown (code POD-07-25). Code or government
      “The depth can vary between gardeners, but 6 inches is the recommended minimum.”
      Checked November 12, 2026. Figures and codes change; verify with the source. Back to where this is used
    5. Raised bed gardens, University of Minnesota Extension, page states "Reviewed in 2026". Code or government
      “The ideal soil mixture for a raised bed is a mixture of around 2/3 to 1/2 topsoil and 1/2 to 1/3 plant-based compost. If the topsoil contains a lot of clay, you may also add some sand to create a more loamy soil texture.”
      Checked November 12, 2026. Figures and codes change; verify with the source.
    6. Raised Bed Gardening (peer-reviewed fact sheet), Utah State University Extension, Published February 2012. Code or government
      “A garden soil blend could consists of equal parts (1:1:1 by volume), of the following ingredients: ... Native soil or topsoil”
      Checked November 12, 2026. Figures and codes change; verify with the source.
    7. Raised Bed Gardening (FS 270), Oregon State University Extension Service, revised September 2020, reviewed 2024. Code or government
      “A cubic yard will cover 162 square feet 2 inches deep ... This creates a soil-and-organic mix about 8 inches deep, sufficient for adequate rooting of most vegetable plants.”
      Checked November 12, 2026. Figures and codes change; verify with the source.

    These are summaries of what the sources say, not professional advice. Codes and product data change. Check with your building department and the product label about your own project.

    Sources

    • [1] Iowa State University Extension and Outreach, What would be a good soil mix for a raised bed? (Yard and Garden FAQ). Checked November 12, 2026. https://yardandgarden.extension.iastate.edu/faq/what-would-be-good-soil-mix-raised-bed
    • [2] University of Maryland Extension (J. Traunfeld), Soil to Fill Raised Beds. Checked November 12, 2026. https://extension.umd.edu/resource/soil-fill-raised-beds/
    • [3] Clemson Cooperative Extension, Home and Garden Information Center, Raised Beds (HGIC 1257). Checked November 12, 2026. https://hgic.clemson.edu/factsheet/raised-beds/
    • [4] Mississippi State University Extension, Constructing Raised Beds for the Mississippi Gardener (P3087). Checked November 12, 2026. https://extension.msstate.edu/publications/constructing-raised-beds-for-the-mississippi-gardener
    • [5] University of Minnesota Extension, Raised bed gardens. Checked November 12, 2026. https://extension.umn.edu/how/raised-bed-gardens
    • [6] Utah State University Extension, Raised Bed Gardening (peer-reviewed fact sheet). Checked November 12, 2026. https://extension.usu.edu/yardandgarden/research/raised-bed-gardening.pdf
    • [7] Oregon State University Extension Service, Raised Bed Gardening (FS 270). Checked November 12, 2026. https://extension.oregonstate.edu/sites/extd8/files/catalog/auto/FS270.pdf

    Made with HoneyDoMath.com. Estimates for planning; check product labels and local codes before you buy or build.