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.

Worked example

A 10 ft × 10 ft garden bed filled 6 inches deep, using bags labelled 0.75 cubic feet and a 10% user-selected allowance. Inputs: Area length 10 ft, Area width 10 ft, Depth 6 in, Volume per bag (ft³) 0.75, Settling & waste allowance 10 %. Result: 2.04 yd³.

Topsoil needed for common projects

Calculated by volume with 0.75 cubic foot bags and a 10% allowance. No bag or bulk weight is implied. Tap a project to load it above.

Method & assumptions

Volume in cubic feet is length times width times depth, with depth converted from inches to feet. We apply the allowance selected by the user and divide by 27 to obtain cubic yards. Bag count is another volume calculation: total cubic feet divided by the volume printed on the selected bag, rounded up to a whole bag.

Bag volume and bag weight are separate product properties. A 0.75 cubic foot bag is not assumed to weigh 40 lb, and multiplying the calculated bag count by an unrelated nominal bag weight would contradict the bulk-density estimate. Enter the actual bag volume for a volume comparison and use the product label for lifting, transport and payload decisions.

Bulk weight is optional because soil density changes with composition, structure and water content. The USDA NRCS method defines bulk density using oven-dry soil mass divided by bulk volume. It does not establish universal “dry”, “moist delivery” or “wet” topsoil weights. If a supplier provides a bulk density for the material and condition being delivered, enter it; otherwise leave it at zero and use the volume result only.

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

Sources and references

These references and structured source records support the method and material data used on this page.

• USDA NRCS: Soil Bulk Density / Moisture / Aeration
• USDA NRCS Soil Quality Test Kit Guide: oven-dry bulk-density method
• NIST SP 811: volume conversion factors

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