How much topsoil do I need before I put down new grass?

Okay, you removed your old, dead lawn - preferably without the use of herbicides. Now you need some topsoil.  You can easily calculate how much topsoil you need from the comfort of your own home.  Here is what you need to know to do it.

• Three things you must know or be able to determine: total gardening square footage, desired topsoil depth, type of planting materials.

Total Gardening Square Footage
To calculate gardening square footage, or area, first break your yard down visually into simple geometric shapes. Then use the following formulas to calculate square footage of each shape:

• Rectangular area: Length x width
• Triangular area: 1/2 Length of one side (base) x length of another side (height). The base and height of the triangle should form an L.
• Circular area: Measure the length of the circle at its widest point (diameter). Divide this number by 2 to calculate the radius of the circle. The area of a circle is calculated by using the formula Πr x 2. Π (pi) = 3.14 and ‘r' = radius of the circle.　

Planting Materials and Topsoil Depth
The type of vegetation being planted greatly impacts how much topsoil is needed. Topsoil depth for a new lawn should be between 3 and 6 inches. Topsoil is sold in cubic feet or cubic yard increments. To calculate cubic foot multiplier, first divide the desired depth of the topsoil by 12. This equals a depth range of 0.25 to 0.5 cubic feet.

　

Cubic Calculations

Multiply your surface square footage by your depth to get the total number of cubic feet of soil needed.

Bulk topsoil is sold in cubic yard increments. To calculate this, divide the total amount of cubic feet by 27, which is the number of cubic feet in a cubic yard.

　

References:

Landscaping in America:Re-establishing a New Lawn

How Much Topsoil for a 12-by-32 Garden?