Roofing Calculator

• •Use the Roofing Calculator when you need accurate results quickly without the risk of manual computation errors or unit conversion mistakes.
• •Use it to verify calculations made by hand or in spreadsheets — an independent check can catch errors before they lead to costly decisions.
• •Use it to explore how changing input parameters affects the output — a quick way to develop intuition and identify the most influential variables.
• •Use it when collaborating with others to ensure everyone is working from the same numbers and applying the same assumptions.

Roofing materials are measured in 'squares,' where one square covers 100 square feet. This calculator determines how many squares and bundles of shingles your roof requires based on its overall dimensions and a waste factor. A standard gable roof has two rectangular planes, while hip roofs, dormers, and valleys add complexity. The waste factor accounts for ridge caps, hip ridges, valley cuts, and starter strips. For standard 3-tab asphalt shingles, three bundles make one square. Architectural (dimensional) shingles are heavier and may require 4 or 5 bundles per square depending on the manufacturer. Knowing your exact bundle count helps you order precisely and budget accurately for your re-roofing project.

• !Measuring the building footprint instead of the actual sloped roof area.
• !Using the wrong number of bundles per square for architectural shingles.
• !Not adding extra material for ridge caps, starter strips, and valleys.
• !Forgetting to budget for underlayment, flashing, and nails.