Soil Calculator and Raised Garden Bed Basics

A soil calculator is definitely essential for raised beds and container gardening. Raised garden beds are becoming increasingly popular as more individuals lack access to plots of ground with loose, fertile soil. Good, quality soil is the single most crucial ingredient for a healthy garden for gardeners. The soil must include vitamins, minerals, and organic matter that can nourish the plants while also allowing their roots to spread.

Soil Calculator

Use our handy soil calculator above to determine the volume of soil needed for specific garden bed dimensions. To use the calculator, you’ll need to measure the length, width and depth of your raised bed.

Here are the steps to take to build an enclosure for your own DIY raised garden bed.

Here are some complimentary ideas for raised garden beds.

Continue reading below to discover more.

Control your Soil

Growing plants in pots or raised beds has the advantage of allowing the growth of wider varieties of plants based on soil types. In other words, you have full control of the soil in your planters and are not restricted by the ground in your yard. You can envisage multiple raised beds with different soil acidity types, for example.

Raised beds and garden pots are also less difficult to maintain. Weeds are less common, and heavy tools like tillers are rarely used. They may be built to fit in any location and filled with fertile soil that is ready for planting.

Soil Calculator for Raised Garden Beds

How Much Soil or Mulch Do I Need?

Most plants need soil that is loosened 12 inches to 18 inches deep. For a raised bed or pot that will be placed on a patio or other hard surface, make sure that the container is deep enough to accommodate root development. To use a raised bed over native soil, be sure to turn the ground with a hoe or garden tiller first.

For instance, if a raised bed is 12 inches deep, the native soil will only need to be turned about 6 inches deep to give the roots plenty of room. However, if the raised bed is only 5 inches deep, the ground under it will need to be turned at least 12 inches deep.

Things to Consider for Calculating Soil Volume

The amount of soil necessary will depend on the size of the raised bed. First, consider what the bed will be used for. Make sure that there is plenty of room to accommodate the number of plants in the raised bed. Different plants require different spacing, so do some research and calculate how much room the raised bed will need.

Also, consider what depth the raised garden should be. Some root vegetables like carrots and potatoes need deep soil to mature underground.

Mulch is a covering layer over soil, and can consist of various materials. Mulch is often made of some organic material, most typically bark, either shredded or chipped. Alternative types of mulch can be grass clippings, leaves, wood chips, straw, or even cardboard. Mulch is useful not just to give garden beds a nicer look, but more importantly, to protect the soil, keep it moist and suppress weeds and other kinds of contamination. Organic mulch is also helping to improve soil quality and richness as it decomposes.

The standard is to have at least 2 inches of organic mulch to cover garden beds and soil. The volume can be difficult to guess so please use our soil and mulch volume calculator above!

Soil Type Basics

After calculating the correct volume of soil to use for a raised bed, the next step is deciding what types of soil most garden beds need. Click this link on how to optimize soil for fruit production. Generally, the ingredients for quality soil are:

  • 60 percent topsoil
  • 30 percent compost
  • 10 percent potting mix

Most Common Types of Soils


Topsoil, as its name implies, is the top layer of soil. The topsoil consists of the top five to ten inches of soil and is rich with organic matter and microorganisms.

Potting Mix

As soil that is designed to work best in pots or containers, potting mix consists of topsoil enriched with forestry products (wood chips, bark, etc.), peat moss, and other nutrients. It holds in water and moisture while still allowing air flow. Incorporating potting mix into container gardens will yield important benefits


Organic matter decomposes into soil, enriching it with nutrients. Compost is the best organic fertilizer and it is important to work compost into garden soil, especially in container gardens and raised beds. Find out more about composting and how worms can help create excellent compost.

Sandy Soil

Sandy soil has lots of tiny sand particles in the dirt. As water passes through the dirt, the sand dries out the water and quickly replaces it with air. Sandy soil is much lighter and looser than clay and does not hold in moisture very well. Carrots, parsnips, and potatoes grow well in sandy soil because the loose particles allow them to expand nicely.

Clay Soil

Dense and often muddy, and retaining water very well, clay soil packs in moisture, but also packs in nutrients. Mulching plants in clay soil can help absorb heavy rains so that the soil does not get too dense. Plants with shallow root systems grow well in clay soil such as broccoli, lettuce, chard, green beans, cabbage, and sweet corn.

Peaty Soil

Peaty soil consists of partially decomposed vegetation and organic matter. It is native to wetlands and grows moss, shrubs, and sedges.

Loamy Soil

Consisting of equal parts sandy, clay, and silty soil, loamy soil merges the unique advantages of different soil types while counteracting the disadvantages. Loamy soil is often the best type of growing soil and can accommodate almost any type of plant.

Can I Reuse Potting Soil?

YES. It is perfectly fine to reuse potting soil from previous seasons. Simply remove any old plants from the container, turn the soil by hand or with a small cultivating tool, and re-plant. If the same soil has been reused for several seasons or has developed a white crust, mix it with some fresh potting soil or add fertilizer to spruce it up.

Raised Garden Bed Basics

There are numerous advantages to building a raised garden bed. First, plant selection is not limited by the region’s natural soil. If a gardener wants to grow beautiful, bright orange carrots but has dense, clay soil in the yard, a raised bed filled with a good mix of loose, sandy soil will do the trick.

Second, compact spaces can be utilized to yield a much larger harvest. Each square inch can be used, and the space is more manageable than traditional garden rows. Companion planting is also much easier to plan and maintain than ever.

When planning the raised bed, take into consideration the manner in which specific plants grow. Watermelon and pumpkin grow along thick, sprawling vines that spread horizontally. Pole green beans and cucumbers climb vertically along stakes or trellises. Tomatoes and some beans are wide and bushy. Research how far apart seeds or seedlings should be spaced and fit as much as possible into the bed.

Choosing the Perfect Location

Most plants require a minimum of 8 hours of sunlight each day. Be sure to build raised garden beds on a sunny site where shade will not hinder their growth. Avoid low lying areas that stay damp and soggy. The proper soil will be well drained, but the garden bed should still not be in a low, wet area. Even though quality soil composed of top soil, compost, and potting mix will not dry out as fast as regular soil, sometimes the garden will require extra watering. Consider where the outdoor faucets are located and whether or not a garden hose can reach the plants to ensure they get a good soaking every so often.

How Big Should A Raised Garden Bed Be?

Size is really a matter of preference, but there are a few factors to take into consideration. The length of the raised bed does not matter, but it is a good idea to keep the width less than four feet. It is important that the middle of the garden be accessible for harvesting and weeding. Generally, a good starting size is 4 long by 4 feet wide. Of course, it can be as long as it needs to be, but since lumber is usually cut in increments of four feet, it is easier if the length is divisible by four.

Ensure that the depth of the raised bed can accommodate root expansion and plant growth. As a rule of thumb, soil should be well-loosened and 12 to 18 inches deep. Six inches is the bare minimum, even for plants with shallow root systems.

Before building the frame for the garden bed, turn the native soil underneath and remove any weeds or grass in the area. How deep the natural soil should be turned will depend on how deep the bed is. If the bed is 12 inches deep, the ground will only need to be turned about 6 inches. If the bed is 6 inches, then the ground needs to be turned at least 12 inches.

Building a DIY Raised Garden Bed

Anyone can build a good raised garden bed with just a few materials and a free afternoon. First, gather the right materials:

  • Wooden stakes
  • Galvanized nails or screws
  • Wooden boards (not railroad ties)
  • Level
  • Hammer or drill
  • Shovel
  • Angle-square
  • Tape measure

After a sunny location has been selected and the site has been tilled and cleared of weeds, follow these steps to construct a raised bed:

  • Rake the ground so that the wall will set flush on the ground.
  • Stake the four corners of the garden bed with one foot 4 by 4 wooden posts.
  • Attach the boards to the corner stakes to build the garden bed frame. Use a level to make sure that the boards are straight.
  • Once the boards are attached, measure the bed diagonally to make sure the bed frame is square.
  • Fill the garden bed with dirt consisting of 60 percent topsoil, 30 percent compost, and 10 percent potting soil.

While acquiring the materials for a DIY raised garden bed is usually simple and cost-effective, there are some kits available for purchase online and at most major retailers. These kits come with everything needed to assemble the garden bed frame and instructions. While the kits may cost a little more, for DIYers that are short on time, the convenience may be worth purchasing a kit. Topsoil, compost, and potting mix can all be purchased in pre-packaged bags. Composting at home is an easy process that takes just a few months, as well. Composting bins are also available on the market that convert waste into organic fertilizer at a quicker rate.

When To Plant

Just as with a traditional garden, do not plant any seeds or seedlings until the final threat of frost has passed. The average final frost date varies from region to region, but it is generally within the months of March through May. To find the average final frost date for a specific zone, refer to the USDA zone map.

Although temperatures are a good indicator regarding planting season, also consider soil temperatures. Typically, seeds that are planted in soil that is still cool, around 50 to 55 degrees Fahrenheit, will germinate within 10 days. For soil that is already 70 degrees Fahrenheit or warmer may germinate in less than 7 days. To determine the soil’s temperature, use a soil thermometer or even a meat thermometer.

Once the seeds have been planted, give them a good drink of water. This is why it is important to consider how far a garden hose can reach when selecting the right location for a garden bed. Some seedlings can benefit from a good, water soluble fertilizer after planting, and then once a month thereafter. We have talked about what to plant in the fall, be it bulbs or vegetables. There are some good tips as well for succession planting to increase your harvest in an easy way.


vRaised garden beds are an excellent alternative to traditional row gardens. They can maximize productivity by allowing more plants to thrive in compact space. They are easy to maintain and weed, and they can be filled with only the best soil for nourishing and housing plants. Gardeners do not have to be limited by lack of space or depleted soil, simply fill a garden bed with rich soil, arrange the seeds or seedlings, and enjoy the harvest!

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