Calculators/Landscaping

Raised Garden Bed Soil Calculator

Estimate how much potting soil or raised bed mix you may need to fill your new garden beds.

Last reviewed: June 2026

ft
ft
in
%

If you are using logs/branches in the bottom (Hugelkultur), lower this (e.g., 50%).

%

Fluffy soil settles heavily after the first few waterings. Add 10-20% extra.

Results update automatically as you enter measurements.

Your Material List

For this project, buy or order approximately

Use these quantities as a shopping list, supplier note, quote check, or quick jobsite material estimate.

Bulk Soil Volume
1.3Cubic Yards
Bags Required
24Bags
Total Volume
35.2Cubic Feet
DIY Mix: Topsoil (50%)
17.6ft^3
DIY Mix: Compost (30%)
10.56ft^3
DIY Mix: Peat/Perlite (20%)
7.04ft^3
Notice: Settling Warning: Fluffy raised bed soil and compost will naturally settle and compress by 10-20% over the first few months and after heavy rains. It's recommended to slightly overfill or keep extra soil on hand.
Estimate note: Actual needs vary due to compaction, grading, cuts, bag yield, and supplier differences. Confirm requirements before purchasing.

Formula and Assumptions

Formula used

Raised bed volume = length × width × height in feet. If you are partially filling the bed, the calculator reduces the height by your fill percentage, then multiplies by the number of beds. A settling factor can be added because fresh soil often compresses over time. Cubic feet are divided by 27 to find cubic yards. For bags measured in quarts, quarts are converted to cubic feet using the standard US dry quart conversion.

Unit conversions

Inches are converted to feet before volume is calculated. Cubic feet are converted to cubic yards by dividing by 27. Bag counts are rounded up because stores do not sell partial bags.

Waste factor explanation

Waste factor helps account for uneven surfaces, cuts, spills, compaction, settling, and measurement differences. The right buffer depends on your project and material.

Material Assumptions and Disclaimer

Bag yield or density assumptions

  • Beds are perfectly rectangular.
  • Assumes standard US dry quart conversion for soil potting bags (1 cubic foot = ~25.7 dry quarts).

Estimate disclaimer

These tools are useful for DIY planning and quick jobsite estimates, but the results are still estimates. Verify quantities for structural work, code requirements, supplier material specs, product labels, or professional requirements before purchasing or quoting a job.

When to be careful

  • Soil inevitably settles over time. Always overbuy or plan to top-dress again in the fall.

Example Calculation

Filling an 8 ft by 4 ft raised bed that is 12 inches tall, 100% full. Using 1.5 cubic foot bags and 10% for settling:

  1. Convert height to feet: 12 inches = 1 foot
  2. Base volume: 8 × 4 × 1 = 32 cubic feet
  3. Add 10% settling factor: 32 × 1.10 = 35.2 cubic feet
  4. Convert to yards: 35.2 ÷ 27 ≈ 1.3 cubic yards
  5. Calculate bags: 35.2 ÷ 1.5 = 23.4 bags
  6. Round up to nearest whole bag: 24 bags needed.

You need 24 (1.5 cu ft) bags or approx 1.3 bulk cubic yards.

Frequently Asked Questions

Can I use regular garden topsoil in my raised bed?

Standard heavy topsoil by itself is usually too dense for a raised bed. It will compact and resist water drainage. You should amend it. A popular standard mix is 50% topsoil, 30% organic compost, and 20% aeration materials (like peat moss, coconut coir, vermiculite, or perlite).

What is Hugelkultur?

Hugelkultur is a raised bed filling method where you place large decaying logs, branches, and organic yard waste at the bottom of a deep raised bed, and only put 6-12 (inches) of quality soil on top. It saves a tremendous amount of money on soil and holds water well, but causes significant soil sinking in the first two years.

How do I convert quarts of potting soil to cubic feet?

Potting soil in the United States is legally measured in "dry quarts". There are approximately 25.714 dry quarts in a cubic foot. So a large 50-quart bag of soil is just shy of 2 cubic feet (1.94 cu ft) while a 32-quart bag is about 1.25 cubic feet.

Should I buy my soil in bags or by the truckload (bulk)?

If you need more than 2 cubic yards of soil (e.g., more than fifty 1.5 cu-ft bags), buying bulk soil from a local landscape supplier is almost always cheaper. They will dump a load of special "raised bed mix" (often a 50/50 loam & compost blend) in your driveway.

Why did my soil level drop so much after a few months?

New potting soil and compost are fluffy and full of air. As you water the plants and gravity takes hold, the soil mechanically compacts. Furthermore, the organic matter inside the soil actively decomposes, physically vanishing into thin air (and into your plants). This is completely normal; just top it off!

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