The short answer
To find how much topsoil you need, multiply length × width × depth in feet and divide by 27 to get cubic yards. A 30 × 20 ft area covered 4 inches deep needs 7.4 cubic yards of topsoil, which weighs roughly 8 tons. For anything over a couple of cubic yards, bulk delivery is far cheaper than bags.
How the calculation works
Topsoil is measured by volume: area × depth. In US units, convert the depth from inches to feet (divide by 12), multiply by the area in square feet, and divide by 27 to get cubic yards. The weight estimate uses a typical 1.1 US tons per cubic yard for dry, screened topsoil.
Worked example
Spreading 4 inches of topsoil over a 30 × 20 ft area for a new lawn:
- 30 × 20 × (4 ÷ 12) = 200 cubic feet
- 200 ÷ 27 = 7.41 cubic yards
- 7.41 × 1.1 = about 8.1 tons
How much soil per 100 square feet
| Depth | Cubic feet | Cubic yards | Bags of 0.75 cu ft |
|---|---|---|---|
| ½ inch | 4.2 | 0.15 | 6 |
| 1 inch | 8.3 | 0.31 | 12 |
| 2 inches | 16.7 | 0.62 | 23 |
| 4 inches | 33.3 | 1.23 | 45 |
| 6 inches | 50.0 | 1.85 | 67 |
| 12 inches | 100.0 | 3.70 | 134 |
How deep should topsoil be?
- Top-dressing a lawn: ¼ to ½ inch, raked into the grass.
- Repairing bare patches: about 1 inch, then overseed.
- New lawn over poor soil: 4 to 6 inches of loam.
- New garden beds: 6 to 8 inches, mixed into the soil below.
- Raised beds: fill to the top, usually 8 to 12 inches, with a soil and compost mix.
Tips
- Test before you buy. A cheap soil test tells you whether you need new soil or just lime, fertilizer or compost.
- Ask for screened topsoil without large stones, roots or clumps.
- Have a spot ready for bulk delivery. A truck tips the whole load in one place, and moving it by wheelbarrow is most of the work.
Frequently asked questions
How much does a cubic yard of topsoil weigh?
Dry, screened topsoil weighs about 2,000 to 2,300 lb (around 1.1 tons) per cubic yard. Wet soil can weigh considerably more, so loads delivered after rain are heavier.
How much topsoil do I need for a new lawn?
Extension guidance suggests adding about 4 to 6 inches of loam where the existing soil is poor. Over good soil, loosening the top 4 to 6 inches and adding an inch or two of topsoil may be enough.
How many bags of topsoil make a cubic yard?
A cubic yard is 27 cubic feet, so it takes 36 bags of 0.75 cubic feet, 27 bags of 1 cubic foot, or 18 bags of 1.5 cubic feet.
How much soil do I need for a raised bed?
Multiply the inside length × width × height of the bed. A 4 × 8 ft bed that is 12 inches deep holds 32 cubic feet, about 1.2 cubic yards.
How much should I add for settling?
Loose soil settles as it is watered and walked on, sometimes by a quarter or more in the first season. Order 10–20% extra for raised beds and fills.
Sources
Related calculators
About this calculator. Every formula on this page is tested against worked examples from the sources above before publishing. Results are estimates for planning; confirm with your supplier or local code.
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