Topsoil Calculator

Tip: loose topsoil settles by 10% to 20% after watering and rain. If the final grade matters, order a little extra and top up after the first few weeks.

Worked example

You are building a new lawn on a 25 ft by 20 ft area and want 4 inches of topsoil under the sod. The area is 500 square feet, and 4 inches is 4 / 12 = 0.333 ft.

500 x 0.333 = 166.7 cubic feet. Dividing by 27 gives 6.17 cu yd of bulk topsoil.

In 0.75 cubic foot bags, the same job would take 223 bags. At that size bulk delivery is far cheaper and saves carrying more than four tons of soil in bags.

How to calculate topsoil

Topsoil is measured by volume. Multiply the length and width of the area in feet to get square feet, then multiply by the depth. Depth is usually given in inches, so divide it by 12 first. The result is cubic feet. Divide cubic feet by 27 to get cubic yards, the unit bulk soil is sold in.

For bags, divide the cubic feet by the bag size printed on the label. Topsoil bags are commonly 0.75 or 1 cubic foot, and garden soil and raised bed mixes often come in 1, 1.5 or 2 cubic foot bags.

How deep should topsoil be?

• Top dressing an existing lawn: 1/4 to 1/2 inch, raked into the grass.
• Filling low spots and leveling: 1 to 2 inches at a time so the grass can grow through.
• Under new sod or seed: 4 to 6 inches over loosened subsoil.
• New garden beds: 6 to 8 inches, deeper for shrubs.
• Raised beds: the full height of the bed, often 10 to 12 inches.

For a project with several depths, run the calculator for each area and add the results together.

Bulk or bags?

Bags make sense for small jobs: filling a few planters, patching bare spots or a single raised bed. Bulk topsoil is much cheaper per cubic yard, but most suppliers have a minimum order and a delivery fee. As a rough guide, once you need more than one cubic yard, which is 36 bags of 0.75 cubic feet, bulk delivery usually wins.

A cubic yard of topsoil weighs about 1 to 1.4 tons depending on moisture and how much clay it holds. Make sure the delivery truck has a clear path and dump the load on a tarp close to where you will use it.

Topsoil, garden soil and fill dirt

Topsoil is the upper layer of natural soil, screened to remove rocks and roots. It is the right choice for lawns and general grading. Garden soil or planting mix is topsoil blended with compost and other organic material, and costs more. Use it for vegetable beds and flower borders. Fill dirt is subsoil with little organic matter, used to raise grade under patios or fill holes, then covered with topsoil.

Ask your supplier whether the soil is screened and where it comes from. Unscreened soil can carry rocks, roots and weed seeds.

Odd shapes and slopes

For curved beds or irregular yards, split the area into simple shapes and add their areas. For areas where the depth changes, such as a slope you are leveling, use the average depth: measure at several points and divide the total by the number of measurements. Our guide to cubic yards, bags and tons walks through these conversions.

Testing your soil first

Before you buy topsoil to improve a lawn or garden, consider a soil test. Many county extension offices test soil for a small fee and tell you the pH and nutrient levels. Sometimes the existing soil only needs compost or lime rather than a new layer of topsoil, which saves money and effort.

More calculators

Results are estimates, not a contractor quote. Check quantities with your supplier before you order, and follow local building codes.