How to Calculate Topsoil Quantity
Area × depth in cubic yards, the right depth for the job, and an allowance for settling
How much topsoil do you need? The short version
Multiply the area in square feet by the depth in inches and divide by 324 to get cubic yards. For example, 1,000 ft² at 4 in is 1,000 × 4 ÷ 324 = 12.3 yd³. Then add an allowance for settling and round up to what your supplier sells.
- Measure the area: length × width, splitting odd shapes into rectangles.
- Choose the depth for the job (see the table below).
- Cubic yards = square feet × inches ÷ 324.
- Add an allowance for settling, then round up.
Area × depth
Topsoil volume is calculated the same way as mulch or gravel: area (length × width) times the target depth, converted to a consistent unit before multiplying, then converted to cubic yards for ordering.
The 324 comes from the unit conversions: 12 in per foot × 27 ft³ per cubic yard. Working in metric, square metres × depth in metres gives cubic metres directly.
Typical depths by use
The right depth depends on the job, and published recommendations are specific about what they apply to. The topdressing row is for compost spread on an established lawn, not a depth of topsoil; it is included because the two are often confused.
| Use | Recommended depth | Source |
|---|---|---|
| New lawn from seed or sod | At least 4–6 in of good topsoil, measured settled | Penn State Extension |
| Compost topdressing on an established lawn (not topsoil) | About ¼ in, worked into the soil | Penn State Extension |
| Raised beds on a hard surface: leafy greens, beans, cucumbers | At least 8 in | University of Maryland Extension |
| Raised beds on a hard surface: peppers, tomatoes, squash | 12–24 in | University of Maryland Extension |
Notes on the recommendations
For a new lawn, Penn State also suggests mixing about 2 in of the new topsoil into the top 2–3 in of the subsoil, so the two layers don't form a sharp boundary. For raised beds on a hard surface, the University of Maryland recommends limiting topsoil to about 20% of the mix by volume, and only in beds at least 16 in deep — so those beds are filled mostly with other growing media, not straight topsoil.
Allow for settling
Loose topsoil settles after it is watered and walked on, and Penn State's lawn depth is the firmed, settled depth. Order more than the settled depth you need. The Topsoil Calculator adds a 10% allowance by default; raise it if the depth you enter is meant to be the finished, settled depth.
Existing grade matters
If you're filling a low spot or grading a slope, the depth isn't uniform across the area — measure or estimate an average depth across the space, or break it into sections like an excavation with varying depth.
For deeper fill and grading, the excavation volume guide covers averaging depths across an area.
Cubic yards or tons
Suppliers quote topsoil by volume or by weight, and the weight of a cubic yard varies with moisture and soil type. Use the supplier's own conversion where you can. The Topsoil Calculator estimates delivered weight from an assumed bulk density of about 1,300 kg/m³ for screened topsoil, which is a planning figure rather than a measured value for your load.
Worked Example
A 1,000 ft² new lawn area, 4 inches of topsoil.
Volume: 1,000 × (4/12) = 333.3 ft³
Cubic yards: 333.3 ÷ 27 ≈ 12.3 yd³
With the calculator's default 10% settling allowance: 12.3 × 1.10 ≈ 13.6 yd³
At 6 in instead: 1,000 × 6 ÷ 324 = 18.5 yd³ before the allowance
FAQ
- How much topsoil do I need for a new lawn?
- Penn State Extension recommends at least 4 to 6 inches of good-quality topsoil, measured after it has settled. Over 1,000 square feet, 4 inches is about 12.3 cubic yards and 6 inches about 18.5 cubic yards, before any settling allowance.
- How do I convert square feet and inches to cubic yards?
- Multiply the square feet by the depth in inches and divide by 324. For example, 500 square feet at 3 inches is 500 × 3 ÷ 324 = 4.6 cubic yards.
- How thick should compost topdressing be on an existing lawn?
- Penn State Extension recommends a thin layer of compost, about a quarter inch, worked into the soil. This is compost topdressing, not a topsoil depth. It warns that repeated thick layers without incorporation can build up organic matter at the surface.
- Should I fill a raised bed on a patio or driveway with topsoil only?
- Usually not. For raised beds on a hard surface, the University of Maryland Extension recommends topsoil as no more than about 20% of the mix by volume, and only in beds at least 16 inches deep.
Related Calculators
Related Guides
Sources
NIST SP 811
Unit conversion reference (cubic feet, cubic yards, cubic metres).
NIST SP 811 — referencePenn State Extension, Lawn Establishment
Minimum 4–6 in of settled topsoil for a new lawn; incorporating topsoil into the subsoil.
Penn State Extension, Lawn Establishment — referencePenn State Extension, Using Composts to Improve Turf Performance
About ¼ in for compost topdressing of established turf.
Penn State Extension, Using Composts to Improve Turf Performance — referenceUniversity of Maryland Extension, Soil to Fill Raised Beds
Raised-bed depths by crop and the share of topsoil in the mix.
University of Maryland Extension, Soil to Fill Raised Beds — reference