Fill in the blanks to determine how many shingles you need. Length of your roof (include overhangs) x Width of your roof (include overhangs) = Sq. feet of your roof x Slope Factor (see chart) = TOTAL + Add 10% for gable roofs, 17% on cottage roofs for hips, ridges and waste = TOTAL / Number of squares needed + Add shingles required for starter (Total length of eave divided by length of shingle) = TOTAL Information provided by: