Concrete Formula for Yardage

Understanding the Formula

• The formula for estimating concrete yardage can be expressed as a simple mathematical formula. In this form, the formula appears as:

  (L x W x D)/27 = CY

  The formula calculates the cubic volume of the area that requires concrete, then divides the volume into cubic yards.

  Measure the length of the area, the width of the area and the depth that the concrete will be poured. Multiply the length times the width to measure the square feet of the surface area. Multiply the surface area by the depth to calculate how many cubic feet of space needs to be filled.

  There are 27 cubic feet in each cubic yard (3 feet x 3 feet x 3 feet). Divide the amount of cubic feet by 27 to estimate the number of yards of concrete needed to fill the area. It is also possible to work the formula in inches, but you will be dealing with much larger numbers. There are 46,656 cubic inches in a cubic yard. This amounts to 36 inches x 36 inches x 36 inches.

Additional Considerations

• Small details can sometimes skew the estimate for the amount of concrete that is needed. A common factor is overexcavation, where you may have spots where the depth is slightly more than what the calculation says. Filling these areas with dirt will help, but it is still a good idea to order a small amount of extra concrete, just to be safe. Most professional concrete workers recommend adding an extra 5 percent to your estimate. In this case, the formula to calculate concrete yardage would be:

  (L x W x D)/27 = CY x 1.05

  Simply take your original calculation for cubic yards and multiply it by 1.05 to estimate the total order with an additional 5 percent.