Use this free soil volume calculator to calculate the amount of soil you need for raised beds, containers, or fill dirt.
🌱 Soil Calculator
This calculator works for both Imperial measurements (feet and inches) and Metric measurements (centimeters and meters).
How to Create Super Healthy Soil for Your Garden Beds
The first thing you need to understand is that all soil can grow healthy plants if you give the soil organisms what they need to create healthy soil. No matter which property I’ve been to with clay, sandy, or silty soil, and no matter how compacted the soil was, I’ve been able to help clients create amazing, lush, rich soil that produces amazing yields within 6 months or less.
The secret for turning poor soil into rich, healthy, amazing soil is to grow lots of healthy plant roots to feed all the soil microorganisms. You can do this quickly and easily using cover crops or pioneer plants if your soil is not immediately suitable for growing tender vegetables. You can also use native plant seeds or allow all the “weed” seeds in your existing soil to germinate and grow.
If you don’t want your “weed” seeds or cover crop seeds to spread, you can terminate the plants before they go to seed and then immediately or soon after plant your vegetable garden.
If your soil is heavily compacted, then you can plant crops that break through compacted soils and open up the soil naturally, creating improved drainage and healthy soil for your veggies and other plants. Here are some great plants for breaking up compacted soil: dandelions, radishes (especially daikon and long-rooted varieties), sunflower, alfalfa, chicory, crimson clover, comfrey, horseradish, sunchokes.
What Kind of Soil Should You Actually Buy?
If you don’t want to wait a few months to build up incredibly healthy soil, then you can purchase soils. If that’s what you want to do, here’s what you need to know:
Topsoil is usually a mix of sand, clay, and silt. It is cheap and good for filling holes in the lawn or leveling ground, but it is not ideal for garden beds. It can be dense, compact easily, and may not drain well, which can suffocate plant roots.
Garden Soil is typically topsoil that has been amended with organic matter like peat moss or compost. It is a better choice for in-ground flower or vegetable beds. However, if you are filling a raised bed, pure garden soil can still become compacted and prevent water from draining properly if it is not mixed with other materials.
Raised Bed Soil is specifically blended for the conditions of a raised bed. It is usually a lighter mix that includes more organic matter (like peat moss, bark, or compost) and is designed to drain well while holding enough moisture. It is less prone to the compaction issues of plain garden soil.
Potting Soil (or Potting Mix) is not actual soil. It is a soilless blend of peat moss, bark, perlite, or coir designed for containers. It is very lightweight and drains quickly. You should never use garden soil or topsoil in a pot, as it will become waterlogged and hard, and you should not use potting soil to fill a large raised bed (it is too expensive and dries out too fast).
Simple Soil Recipe for Raised Beds
If you are filling a raised bed and want to save money by mixing your own soil instead of buying a pre-blended bag, a common recommendation is to use a mix of roughly 60% topsoil, 30% compost, and 10% soilless mix (like potting soil or perlite).
A few notes on this:
Compost provides nutrients and improves soil texture, but you generally do not want it to make up more than about 30-50% of your mix. Too much compost can be overly rich or hold too much moisture.
Topsoil provides the bulk volume.
Soilless mix helps keep the blend light and well-draining.
How Deep Does Your Bed Really Need to Be?
The calculator asks for your bed’s depth, but the ideal depth depends entirely on what you want to grow. Deeper beds cost more to fill, so matching depth to your crops can save you money.
Here is a quick guide based on extension recommendations:
Plant Type Minimum Soil Depth
Herbs, Lettuce, & Leafy Greens: 6 inches
Beans, Peas, & Cucumbers: 8 inches
Peppers, Brassicas, & Root Veggies: 12 inches
Tomatoes, Eggplant, & Squash: 18 inches
A helpful tip: If your raised bed is sitting on the ground (not on concrete), you do not need to fill it with 18 inches of expensive purchased soil for shallow-rooted plants. You can loosen the native soil beneath the bed, and your plants’ roots will grow down into it. In this case, a bed that is only 6 inches tall can effectively provide 12-18 inches of root room for your plants .
A Note on Bagged Soil Math
If you are buying soil in bags, you will notice the bag is sold by weight (like “40 lb”) but the calculator gives you volume (cubic feet). They are not the same thing.
As a general rule of thumb, a standard 40-pound bag of topsoil or compost holds about 0.75 cubic feet of material. This can vary slightly depending on how wet or dry the soil is, so it is usually a good idea to buy one extra bag rather than risk coming up short.
Why Your Bed Might Need a Top-Off Later
It is normal for the soil level in a new raised bed to drop by a few inches after the first season. This happens because the organic matter in the soil slowly decomposes, and rain and watering cause the soil to settle and compact.
Simply top off the bed with fresh compost or garden soil in the spring before you plant.
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