How to Calculate Cubic Yards - Calculating Cubic Yards For Concrete

How to calculate the amount of concrete required? This is the most common question that perplexes people during a home construction. The concrete may be required for the slab/ foundation of your house, or some additional construction like building a backyard patio or a driveway stall. No matter what you need to build up, it is very easy to calculate the cubic yards of the concrete required. All you need is the proper measurement of the area to be constructed and some easy calculations.

What is a Cubic Yard
Cubic yard is a volumetric measurement unit, and the concrete required for construction is measured in cubic yards. One yard is equivalent to 3 feet. Thus, we can formulate the relation between cubic yard and cubic feet as,
1 cubic yard = 27 cubic feet (1 yard = 3 feet)

How to Calculate Cubic Yards For Concrete
The summary of the steps required for calculating cubic yards for concrete are:

• Decide the space that is to be filled by concrete and divide it into smaller shapes if the area is too big.
• Calculate the volume of total area or shapes, accurately by applying the appropriate formula.
• Add or subtract the volumes obtained, accordingly.

Step #1
The height of the concrete poured is usually between 4 inches to 6 inches. Convert this figure in inches into feet. Use the formula,
1 foot = 12 inches
Thus,
4 inches = 4/12 = 0.333 feet
and
6 inches = 6/12 = 0.5 feet

Step #2
Now, find the volume of the total area to be covered by concrete, in cubic feet. Formulas for volume of different shapes,
Square = Length * Length * Height
Rectangle = Length * Breadth * Height

Step #3
Convert the cubic feet figure into cubic yards. As discussed earlier one cubic yard is equal to 27 cubic feet. So, divide the cubic feet volume by 27. The result obtained is the cubic yards of concrete required for the area under consideration.

Example
Let us solve an example to make the procedure of calculating cubic yards for concrete more clear. Suppose that you want to build a foundation for your home. Let the area be rectangular in shape and the dimensions of the area be as follows,
Length = 42 feet
Width = 6 feet
Height of foundation = 4 inches

Step #1
Covert 4 inches into feet. So, height of slab = 0.33 feet.

Step #2
Calculate the volume of the area. So, volume = 42 feet * 6 feet * 0.33 feet = 83.16 cubic feet.

Step #3
Convert 83.16 cubic feet into cubic yard. So, cubic yards for concrete = 83.16 / 27 = 3.08 cubic yard. Thus, you will require 3.08 cubic yards of concrete for the foundation.

NOTE : While calculating the volume, make sure that the units of all the dimensions are in the same unit and the end result is in cubic yards. Use the conversion table.

If you get the figure of cubic yards in decimal, round up the figure to nearest whole number, as the concrete companies provide cement in whole yards. It is always safe to order more quantity than required, taking into consideration a wastage of 10%.