What is a roof's 'slope factor'?

It is the number you multiply a roof's footprint (plan) area by to get the actual sloped surface area. The Roof Pitch Calculator gives it from a rise and run; the Roof Area Calculator applies it.

How do I measure roof pitch?

Measure the vertical rise over a fixed horizontal run (12 units is standard). A roof that rises 6 units over 12 is a '6-in-12' pitch. Enter the two measurements in the Roof Pitch Calculator.

Is the roof-area figure my material order?

No — it is the geometric sloped surface area. The material calculators (shingles, metal panels, replacement cost) take that area and add a product-specific waste allowance, which is shown as a separate, editable figure. Starter courses and ridge/hip caps are ordered on top of the field coverage.

Roofing Calculators

Roofing calculators build on each other. Start with the Roof Pitch Calculator, which converts a measured rise and run into the slope factor — the multiplier that turns a flat footprint into true sloped area. The Roof Area Calculator applies that to your building footprint. From there the Roof Shingle and Roofing calculators convert the area into bundles, squares and accessories, while the Roof Replacement Cost and Metal Roof Cost calculators turn it into a price from rates you enter. Rafter Length and Birdsmouth Cut handle the framing geometry, and the Snow Load and Roof Truss calculators are estimate-only planning tools that carry an engineering-verification notice. A single careful set of measurements feeds the whole category; the roof-area figure is geometry, and each material calculator adds its own editable waste allowance on top.

10 calculators · all live