Instructions: Enter the wall height, length, thickness and approximate square footage of the cellar floor. Hit the "Calculate" button to calculate your estimated number of cubic yards for the wall, the footings and the cellar floor. For "Length" enter the total of the lengths of all foundation walls. measure each wall to the outside ends. Calculate an approximate Square Footage for the cellar floor and enter that figure. Square floorplans are easy (length X Width) but to calculate for odd shapes, break floorplan up into square areas and calculate each. If a section is not a perfect square, calculate as if it were and use that figure. enter the total of all areas. As an example, for a foundation with: