How to Figure Cubic Feet of Top Soil

Topsoil is fertile and rich in organic material.

Topsoil is often lost during landscaping, but good quality topsoil is vital to support healthy plants. Adding new topsoil is the obvious solution since waiting for nature to regenerate the upper soil layers takes far too long. The volume of topsoil required is a function of the surface area to be covered and the desired depth of the topsoil layer. Calculating the volume is a simple task once the area and depth are known.

Instructions

1. Calculate in square feet the surface area requiring additional topsoil. For rectangular and square areas, the surface area is the length multiplied by the width. For odd shaped areas divide the land into a number of small rectangles and add the individual surface areas together. For example, divide an "L" shape plot into two rectangles, and then combine their areas.

2. Determine in inches the depth of additional soil required. The depth may vary according to the intended use. For example, a lawn requires approximately four to six inches of topsoil, though a vegetable garden may benefit from as much as 10 to 12 inches.

3. Multiply the depth in inches by 0.0834, the decimal equivalent of 1/12, to convert it into a decimal value. For example, 14 inches is 1.168 feet -- 14 x 0.834 = 1.168.

4. Multiply the surface area by the depth to calculate the volume of topsoil required. For example, an area of 50 square feet requiring six inches of topsoil requires 25 cubic feet of soil -- 50 x 0.5 = 25.

Tips & Warnings

• Freshly laid soil will settle and reduce in volume. Consider ordering a little extra soil to fill in any depressions that evolve.

• When landscaping commences, save the existing topsoil for use after the job is completed.

• Wet soil may weigh more and have a greater volume than dry soil.

• Topsoil varies enormously in quality; check the soil for weeds, rocks and other debris before purchasing it.

References

• Utah State University Cooperative Extension; Topsoil Quality Guidelines For Landscaping; Rich Koenig
• Kent State University - Web-based Mathematics Education: Area of a Rectangle
• University of Alaska Fairbanks; Establishing a Lawn in Southeast Alaska; Jim Douglas; 2000
• National Gardening Association; Soil Common Sense; Charlie Nardozzi
• California Department Of Transportation: Decimal Equivalents; June 2010
• University of Connecticut; Purchasing Topsoil; Dawn Pettinelli