Calculate the perimeter of the building using the measurements taken with a tape measure and a helper. Measure the distance of each part of the roof. The fascia of the roof is the piece of wood or siding that seals the end of the supports. If measuring the distance from a scale drawing, obtain the final distance by using the correct conversion factor.
Check the perimeter size by taking the raw dimension of the building and adding the number of feet to obtain the extended area of the roof at the corners of the structure.
Calculate material required for the soffit. The amount of soffit material required will equal the amount of fascia with the addition of the area of each corner on the building.
Report the length of fascia in the widths you need. Typical widths of fascia are 6 and 8 inches. As a rule of thumb, always order 10 percent more material than calculated to ensure you have enough material.
Report the amount of soffit required as the number of squares required. The number of squares will depend on the width of the soffit material. Order 10 percent more than required to allow for mistakes. The soffit is always measured in area units.