IB
Institute of Builders

Roof Pitch Multiplier

Plan view square footage is flat. Roofs are angled. Use the pitch multiplier to determine actual surface area for ordering shingles, underlayment, and sheathing.

Include overhangs in this measurement.
Pitch Multiplier Factor
Actual Roof Surface Area

Material Waste Factors

After calculating actual surface area, add waste based on roof complexity:

  • Gable Roofs: Add 10%
  • Hip Roofs / Valleys: Add 15%
  • Complex Custom Roofs: Add 20%