The amount of fabric needed to upholster a sofa is determined by the height, width and depth of the sofa. Use a measuring stick for each of these dimensions to determine specific yards of fabric needed.
A yardstick is equal to one yard of fabric. Measure sofas from all angles, including from the floor to the highest point on the back of the sofa, from the floor to the highest point on the sides of the sofa and across the entire sofa lengthwise. Measure the height and depth of all seat cushions, pillows and matching ottomans with a yardstick to determine how much extra fabric is needed. Multiply length times width and depth times height to get fabric yard measurements.