How much topsoil do I need?
Topsoil is a gardener's best friend. Not only does it provide your plants with all the nutrients they need to thrive, but it also supports root growth, maintains soil structure, retains moisture, and much more. In fact, it’sone of the key ingredients for a garden full of healthy, vibrant plants.
There’s a lot to consider when buying topsoil for your next project, including how much you’ll need. The good news? Finding out is easier than you might think!
At MB Wilkes, we’ve been mastering the art of all things garden-related for almost six decades. Below, we explain the steps you can take to identify the exact volume and depth of topsoil you need for your project.
What is topsoil?
Topsoil is the uppermost layer of soil covering the Earth's surface. As the layer where most of the biological activities of soil occur, it plays a crucial role in supporting plant growth and sustaining ecosystems.
Topsoil is a dynamic mixture of mineral particles (such as sand, silt, and clay), organic matter (decaying plant and animal material), water, and air. Healthy topsoil contains essential nutrients and microorganisms that plants require for their growth.
Topsoil is often confused with compost, but the two are actually very different - topsoil serves as a natural soil layer, while compost is a human-made product that enhances soil fertility through the addition of organic matter and beneficial microorganisms. You can read throughour full guide for a more in-depth comparison of the two.
How to calculate how much topsoil you'll need
Determining the amount of topsoilyou’ll need is fairly straightforward. Here's a simple, step-by-step guide to help you in through the process:
Measure the length and width of the area you want to cover with topsoil. Make sure your measurements are in the same units (e.g. feet, metres).
Determine the depth of topsoil you need. Typical depths for different purposes are:
Garden beds: 6 to 12 inches (15 to 30 cm)
Lawn renovation: 2 to 4 inches (5 to 10 cm)
Filling or grading: Varies based on the project
We’ve explained more about how you can measure the required depth in the next section down.
Calculate the volume of topsoil needed using the formula: Length × Width × Depth = Volume.
If your site has an area of 15m x 30m and needs a coverage of 200mm, for example, you should use this formula: 15 x 30 x 0.20 = 90m3.
Make sure your measurements are in the same units. For example, if you're using feet, your volume will be in cubic feet. If you're using metres, your volume will be in cubic metres.
Once you have the volume in cubic feet or metres, you can determine the number of bulk bags needed by dividing the total volume by the bag's capacity. Keep in mind that bulk bag sizes differ, so be sure to compare the contents of different bags to get the amount right.
If you instead need to calculate the necessary tonnage for buying loose topsoil, make sure to examine the product's bulk density. This density varies based on the specific type of topsoil and its composition.
How deep should topsoil be?
The recommended depth of topsoil all depends on the type of plants you intend to grow, the climate, and the specific characteristics of your land. However, a good rule of thumb is to have a topsoil depth of around 6 to 12 inches (15 to 30 centimetres). This depth providesa sufficient amount of fertile soil for most plants' root systems to establish and thrive.
If the soil is shallow and poor quality, you may want to bring in the recommended amount of topsoil to provide the best growing conditions. To give your plants an even better shot at thriving, think about incorporating compost, organic matter, and nutrients to boost soil quality.
If your existing soil is already good quality, a thinner layer of new topsoil might do the trick, either to achieve the desired depth or to create a level surface with good texture. Don’t forget that some plants, especially those with deep-rooted systems like trees, could use more topsoil depth to really flourish.
Premium-quality topsoils at a price that makes sense
Now that you've got a good handle on how much topsoil you'll need, you can move onto the next step: getting it delivered right to your front door!
At MB Wilkes, we take pride in being Dorset's top choice for high-quality soils and landscaping products. Whether you're in need of one bag or several dozen, you can count on us to supply the perfect topsoil for a thriving garden. Even better? We can do so at some of the most competitive rates on the market!
We offer our soils in both bulk bags and loose, and we're more than happy to work around your schedule as needed during delivery. If you've followed our guide but you're still scratching your head about how much soil to get, don’t worry – we're here to chat about your project and recommend the right option for your needs.