The best way to calculate how much concrete you will need in cubic yards is to do the following. Enter the size of the slab you want to build in square feet. Multiply the thickness in feet by the square footage to determine.
Determine how thick you want the concrete.
Steps to Calculate Cubic Yards of Concrete. The simples use of our tool is as a concrete slab calculator or concrete wall calculator. Click the button to calculate the volume of concrete and man-hours not including mixing needed for this job. One square yard is equal to 9 square feet or an area that is three square feet wide by three square feet long.