Soil Calculator
Calculate how much soil you need for a raised bed or garden plot.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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This calculator tells you exactly how much soil to buy for any raised bed or garden plot, in cubic feet, cubic yards, and bag counts. Here is how to get an accurate estimate:
- Enter your bed dimensions. Measure the inside length and width of your raised bed or plot in feet. A common raised bed is 4x8 feet or 4x4 feet.
- Set the soil depth. Most raised beds need 12 inches of soil for most vegetables. Root vegetables like carrots and parsnips prefer 18 inches. Shallow herbs can do well in 6-8 inches.
- Add a compost percentage (optional). If you are blending soil with compost, enter the compost percentage. For example, entering 30 means your mix is 70% soil and 30% compost. The calculator breaks out exactly how many cubic feet of each you need.
- Read your results. Bag counts round up so you never come up short. Use the 2 cu ft bag count for standard bags sold at garden centers, or the 1 cu ft count for smaller bags.
Results update instantly as you type. Use Share to send your project details to a co-gardener or supplier, or Copy to save the result.
About the Soil Calculator
Soil volume is straightforward: multiply length times width times depth (converted to feet). One cubic yard equals 27 cubic feet, which is the unit bulk soil suppliers use when delivering by the truckload. For smaller quantities, most garden centers sell bagged soil in 1 cubic foot and 2 cubic foot bags. This calculator handles both.
The amendment feature is useful for the popular Mel's Mix and similar square-foot gardening recipes that call for specific ratios of blended materials. By entering your target compost percentage, you avoid buying too much of one material and running short on the other. All calculations run entirely in your browser. No data is sent or stored.
Frequently Asked Questions
How much soil do I need for a 4x8 raised bed?
A 4x8 foot raised bed filled to 12 inches deep requires 32 cubic feet of soil, which equals about 1.19 cubic yards. That is 16 bags of 2 cubic foot soil, or 32 bags of 1 cubic foot soil. If you are using a 30% compost blend, you need about 22.4 cubic feet of soil and 9.6 cubic feet of compost.
How deep should a raised bed be?
Most vegetables grow well in 12 inches of soil. Root vegetables like carrots, beets, and parsnips perform better in 18 inches. Shallow-rooted crops like lettuce, herbs, and radishes can manage with 6-8 inches. If your bed sits on native soil, even 6 inches can work for most crops since roots can grow through the base into the ground below. If the bed sits on concrete or a hard surface, go at least 12 inches deep.
What is the best soil mix for a raised bed?
A common and effective mix is 60% topsoil or garden mix, 30% compost, and 10% coarse sand or perlite for drainage. The Mel's Mix approach uses equal thirds of compost, peat moss, and coarse vermiculite. Avoid filling beds with straight compost, which can compact and become waterlogged. Bags labeled "raised bed mix" or "garden mix" are blended for this purpose and are convenient if you do not want to mix materials yourself.
Is it cheaper to buy bulk soil or bags?
Bulk soil (delivered by the cubic yard) is almost always cheaper per cubic foot than bagged soil once you need more than about 2-3 cubic yards. Most bulk suppliers have a minimum order of 1 cubic yard, and delivery fees apply. For smaller beds, bagged soil from a garden center is more practical even if the per-cubic-foot price is higher. The convenience of driving home with exactly what you need often outweighs the cost difference for one or two small raised beds.