Topsoil Calculator: How Much Topsoil Do I Need?

How to measure for topsoil

1. Map the area. Measure the length and width in feet. For an irregular yard, split it into rectangles and triangles, work out each area, and add them. The square footage calculator guide lists area formulas for triangles and other shapes. Leave out driveways, patios, and planting beds that won't get topsoil.
2. Decide on the finished depth. Use the depth table below. For a new lawn, remember that turf specialists state their numbers as a firmed or settled depth, not a loose one.
3. Measure low spots separately. For a dip or a rut, lay a straight board across it and measure down to the soil at several points. Average those readings and use that as the depth for that patch only.
4. Check the grade near the house. Penn State Extension recommends that lawn areas slope away from foundations at 1 to 4 percent, which is a drop of 1 to 4 feet over 100 feet. If you need to build up soil near the house to get that slope, measure the extra depth there.
5. Enter one area at a time if depths differ, then add the results.

How deep should topsoil be?

The right depth depends on the job. Here is what extension services and product labels recommend:

For raised beds, the math and the soil blend are different; see our raised bed soil guide.

Topsoil per 1,000 square feet

Big lawns are easier to plan in chunks of 1,000 sq ft. Multiply the figure below by your total square footage divided by 1,000.

Example: a 3,500 sq ft lawn area at 4 inches needs 3.5 × 12.35 = about 43.2 cubic yards before any allowance for settling.

Topsoil for common areas

Straight from the calculator, before any allowance for settling. The depths come from the table above.

Topsoil coverage chart: square feet per yard and per bag

One cubic yard of topsoil covers 324 sq ft at 1 inch deep, so divide 324 by the depth in inches for any other depth: 162 sq ft at 2 inches, 81 sq ft at 4 inches, and 54 sq ft at 6 inches. Bags work the same way: a 0.75 cu ft bag covers 9 sq ft at 1 inch, and a 1 cu ft bag covers 12 sq ft.

The 2 inch row matches the Earthgro 40 lb bag, which is rated to cover 4.5 sq ft at 2 inches deep. These are loose-soil figures. Soil settles when you firm or roll it, so add the 10 to 20 percent the calculator note suggests to reach the finished depth.

Bags vs. bulk

Bagged topsoil is handy for patching and small beds. The common bag is 0.75 cu ft; Scotts Premium Topsoil comes in that size, and the Earthgro 40 lb bag is rated to cover 4.5 sq ft at 2 inches deep, which works out to the same 0.75 cu ft. It takes 36 of those bags to make one cubic yard.

Beyond a cubic yard or two, bulk is far less work. When you call a supplier, ask whether the soil is screened, what it contains, and what increments they deliver in. UConn Extension's topsoil buying guide notes that most screened topsoil passes through a 3/4 inch mesh, and that unscreened soil is rarely worth the savings once you count the time spent removing rocks and debris. The same guide estimates about 12 cubic yards per 1,000 sq ft at 4 inches deep, which matches the chart above.

It also helps to know what "topsoil" means on a label. University of Maryland Extension points out that true topsoil is mineral soil made of clay, silt, and sand, and that bagged "organic soil" products typically contain none of it. Scotts sells its Premium Topsoil as a lawn and garden soil conditioner that adds peat moss and organic matter to existing soil. Read the bag so you know whether you are buying mineral soil or an amendment.

Bags of topsoil per cubic yard, by bag size

27 bags of 1 cu ft make a cubic yard; for any other bag, divide 27 by the cubic feet on the label. Go by volume, not weight: a 40 lb bag doesn't always hold the same volume, because soil weighs more per cubic foot when it is wet and less when it is high in organic matter (see the weight table below).

The calculator counts 0.75 and 1 cu ft bags. For 1.5 or 2 cu ft bags, divide the cubic feet it shows by the bag size and round up: the default 20 × 10 ft area at 4 inches is 66.7 cu ft, or 45 bags of 1.5 cu ft and 34 bags of 2 cu ft. At 1,000 sq ft and 4 inches it takes 445 bags of 0.75 cu ft, which is why bulk delivery makes sense for big jobs.

Topsoil weight per cubic yard, dry and wet

About 1 ton per cubic yard when dry and up to about 1.5 tons when wet. The EPA's standard volume-to-weight conversion factors list dry common earth at 70 to 80 lb per cubic foot, loose earth at 76 lb, moist loose earth at 78 lb, and wet earth containing clay at 100 to 110 lb. Penn State Extension works with 82.99 lb of dry soil per cubic foot for a silt loam, and notes that sandy soils are usually denser and organic soils lighter. Multiply by 27 for a cubic yard:

So a ton of dry topsoil is roughly a cubic yard (0.93 to 1.06 cubic yards at 70 to 80 lb per cubic foot), while a ton of wet clay soil is only about 0.67 to 0.74 cubic yard. Water adds weight without adding coverage, so order by the cubic yard; if a supplier sells by the ton, ask how much their soil weighs per yard. Check the payload rating of your truck or trailer before you haul a yard yourself.

Tips for spreading topsoil

• Mix the first layer in. Both Scotts' label directions and extension guidance favor working new soil into the native soil instead of leaving a distinct layer on top. Iowa State Extension notes that distinct soil layers impede water movement and discourage root growth.
• Spread in passes. Dump piles across the area, rake to about half the target depth, then add the rest. It is easier to hit an even grade in two passes.
• Firm before you measure. Water or roll the soil lightly, then check depth again. Fill any spots that sank.
• Keep the slope going the right way. Aim for the 1 to 4 percent fall away from the house that Penn State Extension recommends.
• Test the soil. For a new lawn, Penn State Extension suggests a soil test from a university or private lab three to four weeks before you prepare the ground.

Common mistakes to avoid

• Ordering to a loose depth when you need a settled depth. Lawn specs are firmed depths. Add extra for settling.
• Using one depth for the whole yard. Low spots, slopes, and new beds each need their own number.
• Forgetting the hardscape. Subtract driveways and patios before you calculate.
• Mixing inches and feet. The depth field is in inches. Entering 0.33 (a third of a foot) gives a result twelve times too small.
• Burying seed. When covering new seed, a thin layer is enough; the Ask Extension answer suggests about 1/4 inch.