How Much Soil Is Needed for Raised Garden Beds, Formula to Calculate Soil Volume for Raised Garden Beds

How Much Soil Is Needed for Raised Garden Beds, Formula to Calculate Soil Volume for Raised Garden Beds

Many people are interested in elevated gardens because of the countless benefits they offer. Some of these benefits include more control over soil type and conditions, the convenience of using the square footage method, and fewer weeds. Best of all, you can fill your raised bed soil with your own custom mix if the native soil isn't conducive to plant growth.

If you're thinking about making a DIY raised garden, then you need to take every step of the process seriously. Filling raised beds with soil is an important step in planting. To avoid waste and save money, it is important to calculate the amount of soil needed. Below is a formula for calculating the required soil volume, depending on the size and shape of the raised bed. For your convenience, we have attached a table with the corresponding indicators for our garden beds so that you can easily calculate the amount of soil you need.

formula for calculating soil volume

The formula for calculating the amount of soil varies depending on the shape of the raised bed. Before jumping into the formula, you need to know what units of measurement are required. For the calculation, you need to find the right bed size and then convert them to common units. For example, if the volume measurement is in feet, first convert the appropriate measurement of the bed to feet.

Raised Bed Square/Rectangular Soil Volume Formula

The formula for soil volume in a rectangular bed is very simple and involves only three measurements. You can also refer to the product page for the volume of each configuration in the standard kit.

V = length x width x height

V represents the volume of soil you need to fill.

L is the length of the loft bed.

W is the width of the loft bed.

H refers to the height of the loft bed.

1. Measure the length, height and width of the bed. Remember to convert the measurements to the same units. For example, if your bed is 17 inches, divide by 12 to get 1.4 feet.

2. Multiply the measurements.

3. Divide the number by 27 to convert it to cubic yards, as bulk soil is usually sold by the yard.

Round Loft Bed Recipe

To calculate the area of ​​a round loft bed, you need to know the radius and height of the bed, which you can check on the product page. The radius is half the diameter of the circle. Square the radius, then multiply by 3.14. Finally, multiply the quantity by the height to get the volume.


Calculate Soil for Geometric Beds

The formula below works for a hexagonal raised bed, when the bed is a regular hexagon (meaning the sides are all the same length).


V is the total volume of soil

S equals the length of one side of the regular hexagon

H equals the height of the bed

Soil Depth for Raised Beds

The amount of soil required also depends on the type of plants you wish to grow. Plants with deep roots need more soil, while other plants need shallow soil to cover their roots. If you find all these calculations cumbersome, you can buy ready-made raised garden bed kits from a reliable source for easy planting.

The following plants have 12-18 inch roots

Garlic, Onion, Leek

Lettuce, Brussels Sprouts, Spinach

Corn, Cabbage, Radishes


The following plants have 18-24 inch roots

beans, peas

Cantaloupe, Pumpkin, Eggplant

carrots, radishes, beets


The following are plants with deep root systems of 24-36 inches

artichokes, asparagus

Parsnips, Rhubarb

sweet potato, pumpkin


The advantage of raised garden beds is that you can grow plants at half the depth you would normally need, so you can grow almost everything on the above list in our 17-inch and 32-inch beds. You can mix and match vegetables according to your tastes and preferences, and make sure to keep them separate.

What is a mulch and why do I need it?

Mulch is the layer that covers the soil, usually made of organic material. It's usually made from chopped bark, but alternatives can include grass clippings, leaves, wood chips, or straw. Mulch is used to improve the aesthetic appearance of garden beds and to protect soil by keeping it moist and inhibiting weed growth. Organic mulch can be used to improve soil quality and richness.

It is important to replenish the soil in the garden bed to ensure it does not run out of nutrients. Adding organic matter to the soil is essential in order to keep the soil healthy. You can add chopped leaves to the soil in the fall and compost in the spring. Consider starting composting so you can reduce both waste and the amount of fertilizer you need.

Soil mixes suitable for raised beds

For good drainage, you need to use premixed soil. Vegetables, fruits, and herbs require a nutrient-rich, light-weight soil mix, usually consisting of the following ratios:

60% high quality soil

30% compost material

10% Soilless Additives

You can experiment with this ratio to see which mix works best for different crops. Garden soil should not fill the entire bed as it is too heavy to drain well. You should add half of the potting soil to the mix for best results.

How to Prevent Weeds

You should add material to the bottom of the bed to prevent weed growth. Cardboard can be used as it is an inexpensive, readily available solution to form a weed barrier while still being porous enough for good drainage. However, it degrades rapidly. If you want a longer-lasting solution, you can use a landscape fabric or hardware cloth to deter weeds and pests like gophers and moles.

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