Topsoil Calculator

This is an estimate, not professional advice. Check your inputs and verify the result against your plans and local building code before you build or order. See terms and disclaimer.

How this calculator works

Enter your dimensions and the result updates instantly. A waste allowance is included so you order slightly over rather than running short mid-pour, and ready-mix is rounded up to the nearest quarter yard, which is how it is sold.

Worked example

A 10 ft × 10 ft garden bed filled 6 inches deep with moist, average-density topsoil, and a 10% settling allowance. Inputs: Area length 10 ft, Area width 10 ft, Depth 6 in, Soil condition 2, Settling & waste allowance 10 %. Result: 2.04 yd³.

Topsoil needed for common projects

Calculated with moist/average topsoil (2,400 lb/yd³) and a 10% settling allowance. Tap a project to load it in the calculator above.

Method & assumptions

We find the volume of the area you are filling, then convert it to weight using the density of the soil condition you picked. Volume in cubic feet is length times width times depth, converted from inches to feet, and cubic yards is that figure divided by 27. According to the USDA Natural Resources Conservation Service, bulk density in undisturbed soils typically runs 1.0-1.4 g/cm3, which converts to roughly 1,680-2,360 lb per cubic yard. Commercial, screened topsoil usually sits at the heavier end of that band and above it, because screening removes the large air pockets and rock left by native soil, and moisture adds weight fast: water itself weighs about 62 lb per cubic foot. That is why we offer three presets: dry/loose screened topsoil at about 2,000 lb/yd3 (1.00 ton), moist topsoil at typical delivery moisture around 2,400 lb/yd3 (1.20 tons), and wet or compacted soil up to about 2,800 lb/yd3 (1.40 tons).

Bag counts use the standard U.S. bagged-topsoil size: a 40 lb bag holds about 0.75 cubic feet, confirmed on both The Home Depot's and Lowe's product listings, which works out to about 36 bags per cubic yard. We round bags up, since you cannot buy a partial bag, and use an epsilon before rounding so exact multiples (such as 75 ft3 landing on exactly 100 bags) do not get bumped up by floating-point error.

The settling and waste allowance covers two things: normal spillage and an uneven subgrade, plus the fact that loose, freshly spread topsoil compacts once it is watered and rained on and loses some of its loose volume. A simple top-dressing only needs about 10% extra. A new bed that gets tilled into the native soil, or a raised bed filled from empty, settles more as it waters in, so plan on 15-20% extra so you are not short a few weeks later. Depth should match the job: 1-3 inches is enough to top-dress an existing lawn or smooth low spots, 6 inches is standard for a new garden bed over native soil, and raised beds typically run 6-12 inches deep, going deeper for root crops. Below roughly one cubic yard, bagged topsoil from a home center is usually more practical than arranging a bulk delivery, which the result flags automatically.

Pro tips and common mistakes

• Loosen the subgrade first. Till or scarify the top 2-3 inches of the existing ground before adding new topsoil. Dumping loose soil over hard, compacted ground creates a layer boundary that traps water and stops roots from growing down into it.
• Buy a little extra for settling. Freshly spread topsoil compacts once it is watered and rained on. The 10-20% settling allowance in this calculator covers that, so measure your target finished depth, not the loose depth you plan to dump.
• Match the depth to the project. 1-3 inches is plenty to top-dress an existing lawn or level low spots. Use 6 inches for a new garden bed, and 6-12 inches for a raised bed, going deeper for root vegetables like carrots and potatoes.
• Do not fill raised beds with pure topsoil. A common mix is roughly 40% topsoil, 40% compost and 20% coarse sand or perlite. Straight topsoil compacts hard in a contained bed and drains poorly compared with a blended mix.
• Keep the grade below siding and pavement. Finished soil should sit at least 6 inches below wood siding and slope away from the foundation. Piling topsoil too high against a house invites moisture damage and pests.

Frequently asked questions

References

• USDA NRCS: Soil Bulk Density / Moisture / Aeration
• Topsoil (Wikipedia)
• SDSU Extension: Bulk density as an indicator of soil health

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