If you're pouring a concrete foundation, cellar floor, or garage floor, how do you figure out how much concrete you need? There's a pretty simple formula: take the length in feet, times the width and height of the wall to figure your cubic footage. Then divide all that by 27 to get your cubic yards, because there are 27 cubic feet in a cubic yard. Most cement trucks hold between 8 and 14 cubic yards, and an average house with a full foundation will take about four truckloads.