Construction & Materials · Verified formula
Topsoil Calculator
Work out how many cubic yards, bags and pounds of topsoil your garden bed or lawn project needs.
Formula verified
3+ known-answer test cases
Last verified August 2026
Result
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How to use the Topsoil Calculator
- Choose rectangular or circular to match your bed or lawn area.
- Enter length and width (or diameter) in feet.
- Enter your target fill depth in inches — 3-4 in for lawn top-dressing, 8-12 in for raised beds.
- Adjust density and bag size if your supplier lists different figures.
- Select Calculate to see cubic yards, weight and bag count.
Formula
Volume
Volume = surface area × depth (then converted to your chosen units)
Assumptions: Default density (1.1 tons/yd³) is a typical figure for screened topsoil. Moist or compost-heavy soil can weigh noticeably more. This tool provides a general estimate, not professional, engineering, tax or legal advice.
Worked example
Verified example
QA passed
Area: 20 ft × 10 ft rectangular Depth: 3 in (0.25 ft) Volume = 20 × 10 × 0.25 = 50 ft³ Cubic yards = 50 ÷ 27 = 1.8519 yd³ Result: 1.8519 yd³ of topsoil needed
Why this matters: Getting fill depth right affects whether new grass or garden beds actually establish — too shallow a layer and roots hit compacted subsoil before they get established.
Common mistakes
- Measuring depth in the wrong unit and ending up off by a factor of 12.
- Assuming all topsoil bags hold the same volume — bag size varies by brand and needs checking against the label.
- Not accounting for settling after the topsoil is watered in, which can reduce the finished depth by 10-20%.
Frequently asked questions
How deep should topsoil be for a new lawn?
Most new lawns need 4-6 inches of topsoil over the existing grade. Raised garden beds are usually filled 8-12 inches deep.
How many bags of topsoil equal a cubic yard?
A standard 40 lb bag holds about 0.75 cubic feet, so roughly 36 bags fill one cubic yard. Bulk delivery is almost always cheaper past a few cubic yards.
Does topsoil weight vary by moisture?
Yes, significantly. Dry topsoil is lighter than screened, moist topsoil. Use the weight estimate as a planning figure, not a delivery-ticket guarantee.
Related calculators
Formula reviewed against the site calculation methodology.
Read our formula reference library or report an issue via contact.
For more background, see Tons vs Cubic Yards: How Material Weight and Volume Relate.