When planning a construction project, it's important to order the correct amount of materials, including concrete. If you order too much concrete, you're wasting money; if you order too little, you will be unable to complete the project. When purchasing concrete, the measurement used is cubic yards. If you're installing curbs and gutters, calculating the amount of concrete you need for the project is fairly easy if you have the correct formula.

Measure the length, width and height of the gutter or curb. Use feet as the unit of measurement, so if the height is 6 inches, convert it to .5 feet.

Multiply the length, width and depth together to determine the volume.

Divide the volume of the gutter or curb by 27, the number of cubic feet in a square yard.

Add 10 percent to the number of cubic yards to provide for a spillage allowance by multiplying the number of cubic yards by .10.

Add the spillage allowance to the number of cubic yards needed for the project.