A Soil Calculator for Raised Beds and Containers
- determine how much soil you need -

Posted on May 4, 2022

A Soil Calculator for Raised Beds and Containers
A soil calculator for raised beds and potted plants can help you avoid frustrating mistakes when setting up your beds or containers. Have you ever gone to the garden center and guessed at how much potting soil or raised bed soil to buy? If so, you likely brought home too little or too much.

The good news is that you don't need to be a math whiz to use a soil calculator formula and ensure that you get the right amount. We've answered some common soil volume questions here and provided the tools necessary for you to do your own calculations. We've also found a great online calculator you can use if you prefer.

Soil Calculator - How much soil do I need?


man scooping potting soil from a wheelbarrow and using it to fill two large pots
The calculations provided here will allow you to buy the right amounts to fill your containers or raised beds, but how much it takes to fill them initially is not the only factor to consider. High-quality potting and raised bed mixes are loamy, meaning they are aerated and will pack down to some degree with watering.

As you make your determinations on how much soil you'll need using the information we've provided, err just a bit on the high side so that you'll have a little left over to add after your soil has settled. Adding about 15 percent to your final calculations should provide you with an adequate buffer.

How much soil do I need for a raised bed?


woman dumping a wheelbarrow load of garden soil into a newly built raised garden bed
Most raised beds are square or rectangular in shape, which makes it easy to calculate how much soil is needed to initially fill them. Here's the formula if you'd like to do it yourself:

How much soil for raised bed = length X width X depth


So, if your bed is 10 feet long, 6 feet wide, and two feet high, 10 X 6 X 2 = 120 cubic feet of soil. Larger bags of potting soil are often labeled according to cubic feet with most being offered in 2 cubic foot bags. If you're filling a 120 cubic foot raised bed, you'll need 60 bags (4.4 cubic yards) of soil.

That's a lot of bags! It may be easier and cheaper to buy in bulk. Local landscaping supply stores sell by the cubic yard and many deliver if you don't have a truck.

How much potting soil do I need?


lots of large terra cotta pots filled with a colorful variety of flowering plant combinations
If you're filling round pots the calculations necessary to answer this question can be a bit involved, so we'll avoid them and give you direct answers. Based on their top diameters, here are the soil amounts required to fill the most common sizes of round pots:

  • 8 inch (20 centimeter) - 1 gallon (4 quarts or 3.8 liters) - 0.15 cubic foot
  • 10 inch (25 centimeter) - 3 gallons (12 quarts or 11 liters) - 0.46 cubic foot
  • 12 inch (30 centimeter) - 5 gallons (20 quarts or 19 liters) - 0.77 cubic foot
  • 14 inch (36 centimeter) - 7 gallons (28 quarts or 26.5 liters) - 1 cubic foot
  • 16 inch (41 centimeter) - 10 gallons (40 quarts or 38 liters) - 1.5 cubic feet
  • 20 inch (51 centimeter) - 17 gallons (68 quarts or 64 liters) - 2.3 cubic feet
  • 24 inch (61 centimeter) - 25 gallons (100 quarts or 95 liters) - 3.3 cubic feet

How about an online garden soil calculator for raised beds and containers?


woman using a soil calculation app on her smart phone
If you really hate math, don't worry. You can use an online tool to automatically calculate how much soil you need. You simply enter the length, width, and depth measurements for square or rectangular raised beds or containers, select how you want the results displayed (cubic feet, cubic yards, centimeters, or liters), and click a button.

Most square and rectangular containers taper inward toward the bottom so the calculation result using this tool will be a bit high, but remember that you'll need some extra soil to account for compression after potting and watering.

The best soil for pots and raised beds


gloved hands putting potting mix in a small terra cotta pot to plant a primula flower
Whether plants are in containers or raised beds, their health will be affected by the quality of soil you use. If you're unsure about which soil mix will produce the best results for your specific application, you're in luck. We have tips that will help you make the right soil selection. And, if you're looking for the right location for raised beds, make sure you select a spot that gets enough sun by measuring the sunlight in your landscape.

raised garden bed made from wood planks and filled with vegetable plants and marigolds

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