Pitch Multiplier

Definition

The pitch multiplier is the factor used to convert a roof's footprint (the area of the ground it covers) into its actual surface area. A flat roof has a multiplier of 1.0. A 6/12 pitch has a multiplier of approximately 1.118. A 12/12 pitch is 1.414. You calculate it with the formula: multiplier = √(rise² + run²) / run. Missing the pitch adjustment is one of the most common estimating errors because it always causes you to under-order materials and under-bid the job.