The topsoil calculator turns an area and a depth into cubic yards and a count of 0.75-cubic-foot bags, so a bulk delivery and bagged soil can be priced side by side.
Depth is the decision. New Mexico State University's turf guide puts the absolute minimum soil depth for a lawn at 4 inches and recommends 6 or more; if some of that depth is already good soil, you only buy the difference.
How to use it
- 01
Measure the lawn or bed
The ground to cover, in feet. An L-shaped yard is two rectangles: run each and add the bags.
- 02
Enter the depth to add
Enter what you will add, not the total. NMSU's guide adds topsoil to reach 4 to 6 inches after firming; Clemson Extension suggests adding up to 3 inches where the soil is clayey or eroded.
- 03
Set a waste allowance
Ten percent by default. NMSU measures its depths after firming, and loose soil firms down, so keep the allowance.
How the math works
Volume
Four inches over a 20-by-10 lawn is 66.7 cubic feet of soil, 20 × 10 × 4 ÷ 12, or 2.47 cubic yards once divided by 27.
Bags
Bags = cubic feet × (1 + waste) ÷ 0.75, rounded up, for the 0.75-cubic-foot bag Scotts sells. The same lawn with ten percent waste needs 98 bags; a cubic yard is 36.
Bulk or bags
Bulk topsoil is sold by the cubic yard and arrives as a pile. Enter the yard's price and the bag price, and the calculator totals both ways.
Where the number goes wrong
- Entering the total depth when some good soil is already there. Measure it, and add only the difference.
- Spreading topsoil over subsoil compacted by grading. Clemson Extension says that compacted layer must be broken up first.
- Burying tree roots. Clemson warns that trees can be suffocated by deeply covering their roots with soil.
- Grading toward the house. Illinois Extension keeps the final grade at a 1 to 2 percent slope away from buildings.
Questions people ask
How deep should topsoil be for a new lawn?
NMSU's turf guide puts the absolute minimum at 4 inches of soil and recommends 6 or more for deep roots. Where the soil is clayey or eroded, Clemson Extension suggests adding up to 3 inches.
How many bags of topsoil are in a cubic yard?
36 bags of 0.75 cubic feet, since a cubic yard is 27 cubic feet.
How much area does a bag of topsoil cover?
Scotts puts its 0.75-cubic-foot bag at 4 square feet at 2 inches deep; at 4 inches, half that.