How Much Topsoil Do I Need?

So, you are looking around your local landscaping store at all the bags upon bags, rows upon rows, of topsoil. And you’re wondering: How much topsoil do I need? Do I even need topsoil? How do I get one of those 50-pound bags off the top shelf? Most of those are very important questions! How do you justify buying dirt when you’ve got free dirt on the ground at home already? If you do buy topsoil, you don’t want to buy too little and need to make a return trip, or use too much and ruin your yard. So, how much topsoil do you really need for your project? Let’s talk about it.

Why do you need topsoil?

Buying quality soil for your projects is extremely important. Like most people, you are probably not familiar with, or are new to the world of landscaping and gardening, so it is important you learn about topsoil. But why buy topsoil? Your garden is already made of dirt, why not just till it, dig some holes, and plop your plants down?

Topsoil plays an important role in getting your plants started on the right foot. Nutrient-rich topsoil is vital to helping your plants grow and reach their full potential. They need good quality soil in order to develop strong root systems and thrive in your lawn or garden. Normal dirt can be lacking in these nutrients or can be sandy and let the moisture escape before your plants can get a drink. You may also have clay in your dirt, which can suffocate your plants. 

If you don’t know what kind of dirt you have and just plant, you’re gambling all the money you just spent on plants. And those odds aren’t always great. Good topsoil can provide fertilization and can help retain moisture to help your plants. So don’t risk your lawn and your money on your home dirt and get some topsoil.

How much do I need for a garden or flower bed?

If you’re trying to get fresh fruits and veggies, or maybe trying to add some curb appeal to those planters at the front of your house, you don’t need a lot of bagged topsoil. If you’re trying to fill a new garden bed, it’s recommended you have eight inches of topsoil to fill the bed and give the plants the nutrients and room they need to take root. 

If you are planting flowers, you don’t need a thick layer as the roots don’t need as much room to grow, and you can have a thinner layer of topsoil. Just be sure to do research on what types of soil your specific plants and flowers prefer, and what depths they like to grow at.

For shrubs and trees?

If you’re trying to plant trees or shrubs, the level of topsoil varies. For trees you’ll need a large amount to make sure the roots are able to sink down deep and grow, but shrubs don’t require that same depth since they don’t get very tall. 

The exact amount depends on how many trees you plan to grow, and how large they get at maturity. For saplings you really only need about four inches to pack around the roots, but same as the smaller plants you need to look into the species you’re planting to see what they prefer to grow in. 

For grass and sod?

If you are laying down grass, you don’t need that much topsoil. If you’re laying down sod all you need is a thin 3-inch layer to help the new sod take root in your yard and thrive.

If you’re laying grass seed, topsoil is wonderful for helping it take root and begin to flourish. Like for the sod, you only need a few inches to let the grass grow healthy and take root, but the topsoil can also be used to help even out your lawn and avoid puddles that can rot your seeds when watering your new grass.

If you plan to just fill in a few gaps in your landscaping, all you’ll need is enough to fill in those gaps. 

What else can I use topsoil for?

Topsoil is helpful for more than just providing nutrients and a moisture-rich environment for your plants, having extra dirt on hand for your projects is never a bad thing. If you’re spreading mulch, for example, you can lay down a thin layer of topsoil to help hold the mulch in place. Just lay some topsoil down before you add the mulch, and sprinkle some on top after, and your mulch will stick down and not wash away so easily. 

How do I calculate how much topsoil I need?

Now it’s time for the exact math. By now you have a good idea of how many inches of topsoil are required for your projects, but you still have no idea how many bags you need. Luckily for you, there are plenty of helpful calculators online that can do that math and even tell you how many bags you’ll need! 

However, if you’re rearing to go and are handy with a calculator and something to measure your area with, here’s how it breaks down: For ease of explanation, let’s say you’re filling a garden bed. You will need to multiply the length and the width of the bed in feet, by the depth of the soil you need. Length x Width x Depth = The cubic feet of your garden bed. If you’re working with inches, divide them by 12 to calculate feet. 

So, if your garden was 5 feet long, 5 feet wide, and you needed 3 inches of topsoil, you’d divide 3 / 12 to get .25ft, and then it would be 5ft x 5ft x .25ft = 6.25 cubic feet. 

Then all you’ve gotta do is compare that to the size of the bag of topsoil you’ve set your heart on, and you’re set! All that’s left to do now is to figure out how to get that fifty pound bag of soil off the top shelf.