How to Determine Cubic Yards Needs

Determine the area you need the materials to cover. The calculation of cubic yards is independent of what type of material you are discussing.

Measure the area where you will place the material. For materials such as soil, mulch, gravel and sand, measure the length and width of the proposed location. If there are multiple sites where you will place the material, you must include each of these areas in your total estimate of coverage area. For example, assume you desire to cover your driveway -- 20 feet-by-30 feet -- and the walkway -- 6 feet-by-30 feet -- with gravel.

Decide how deep you want the material after the even spreading has occurred. Typically, this measurement is in inches. You may desire a gravel bed 6 or 8 inches deep in the driveway, but on the walkway you only need the gravel 4 inches deep.

Sum together the total volume of material required by the project. Convert all measurements to feet and multiply length times width times depth to obtain the total volume of material. Driveway volume equals 20 feet times 30 feet equalling 600 cubic feet at a 1/2 foot deep. The walkway volume is calculated as walkway volume equals 6 feet times 30 feet equals 180 square feet of gravel 4 inches deep. Convert the 4 inches deep to feet by dividing by 12. 4 inches / 12 inches / foot = 0.33 feet. Total volume of gravel needed is 0.33 cubic feet plus 180 cubic feet which equals 180.33 cubic feet.

Convert the number of cubic feet to cubic yards by using the conversion rule, 1 cubic yard equals 27 cubic feet. 180.33 / 27 = 6.67 cubic yards.