= 322.4 sq. ft. of total gable area. Add this to the 1260 sq. ft. figured for the walls, above. 1260 sq. ft. + 322.4 sq. ft. = 1582.4 square feet of total siding. 1582.4 sq. ft. divided by 100 sq. ft (1 square) = 15.82 squares. Round this up to 16 squares. You notice that we did not deduct for openings and always rounded up, so there is no need to add back to the estimate for cutting waste. 16 squares will do this job. Estimating for Soffit Soffit material will be used on the front and rear eaves, the gable overhangs, the dormer overhangs and any porch ceilings. Calculating the Eaves For the front and rear eaves, add the total length of each section and multiply by the width. The width is a straight-line distance from the wall to the tails of the rafters. This would also be done on the ends of the home on a hip roof. Our sample home in GENERAL ESTIMATING TIPS was 40' long with a 12" overhang on each of its two gables. Total length of the home then, would be 42'. If the overhang is 12" on both the front and the rear eave, then the square footage of soffit needed is 42' x 1' = 42 sq. ft. The back is a duplicate of the front so the total is 42 sq. ft. + 42 sq. ft. = 84 sq. ft. These low eaves will require vented soffit for attic