Soil Depth

The amount of topsoil per square yard that you want to add depends on one important factor. You need to know how deep you want the topsoil to be. If you choose to top-dress your existing lawn with a fresh layer of topsoil, consider that you need to add enough topsoil to equal 1 inch in depth. If you prepare your yard for a new lawn, you should add 4 to 6 inches. If you prepare a yard for a new sodded lawn, you want the topsoil depth to be 3 to 5 inches. When using topsoil for a vegetable garden, you want the depth to be 8 to 12 inches.

Calculating

Because there are variables in how much topsoil needs to be added for various purposes, you need to do some math to determine precisely how much topsoil to add per square yard. Start by measuring the length and width of the area you wish to cover to establish the square footage. Several websites provide special programs that help you with calculations. You simply input the square footage and the depth you desire. The calculator program then determines how many cubic yards of topsoil you need to buy. Divide your square footage by the total number of cubic yards of topsoil recommended to establish the amount you need to use per square foot. Then convert from square feet to cubic feet by multiplying the figure by .11 (point 11).

Square Yardage

A 50-foot-by-50-foot area with a topsoil depth of 1 inch requires 7.716 cubic yards of topsoil. That equates to one cubic yard of topsoil per 324 square feet. That equals one cubic yard of topsoil per 35 square yards of lawn. Essentially, one square yard in this case would require 2/100 of a cubic yard of topsoil. You would use 1/10 of a cubic yard per square yard of lawn if you were adding topsoil to a depth of 4 inches.

That, of course, is difficult to measure. The easier way to handle the issue is simply to use the online calculators to determine the amount of topsoil you need for your specific purpose. Then you only need to be sure you add it to the recommended depth. Raking the topsoil can help to level it after application.