Roof Pitch Calculator

The Roof Pitch Calculator is a free online tool for calculating roof pitch, angle in degrees, slope percentage, and rafter length from rise and run measurements, hosted on RoofAngler.com.

What is the Roof Pitch Calculator?

It takes user-provided rise and run (in inches) and an optional roof span (in feet) to compute the pitch ratio, angle in degrees, slope percentage, rafter multiplier, and rafter length. Results are displayed alongside an interactive cross-section diagram. The tool is fully web-based, requires no installation, and is free to use.

Key Features

• Rise and run input — Enter vertical rise and horizontal run in inches to calculate pitch ratio, angle, and slope percentage.
• Rafter length calculator — When roof span is provided, the tool outputs the exact rafter length for that pitch.
• Interactive diagram — A visual roof cross-section updates in real time as values are entered.
• Reference chart of common pitches — Includes 12 standard pitches (e.g., 4:12, 6:12) with their degrees, slope percentages, rafter multipliers, categories, and typical uses.
• Mobile-friendly interface — Works on phones, tablets, and desktops without app download.
• FAQ and related articles — Built-in frequently asked questions and links to blog posts about shed roof pitch, calculation methods, and pitch factors.

Who is it for?

• Roofing contractors — Quickly compute rafter lengths and pitch angles for estimates and on-site work.
• Homeowners planning DIY roofing — Determine the pitch of an existing roof or check requirements for shingles (minimum 4:12 for asphalt).
• Architects and engineers — Reference standard pitch categories and degrees for design specifications.
• Construction students — Learn the relationship between rise, run, pitch ratio, and angle through an interactive tool.

What can you do with it?

• Calculate rafter length for a new roof — Enter the rise, run, and span to get the exact rafter measurement for cutting.
• Compare common roof pitches — Use the built-in chart to see degrees, slope percentages, and rafter multipliers for 1:12 through 16:12 pitches.
• Convert between pitch formats — Input rise and run to get the pitch ratio (e.g., 6:12), angle in degrees, and slope percentage all at once.
• Validate existing roof measurements — Check if a roof meets minimum pitch requirements (e.g., 4:12 for asphalt shingles, 2:12 for modified bitumen).

How does it work?

1. Enter the rise (vertical) and run (horizontal) in inches. 2. Optionally enter the roof span in feet to calculate rafter length. 3. View the results: pitch ratio, angle in degrees, slope percentage, rafter multiplier, and rafter length. 4. An interactive diagram updates automatically to reflect the inputs.

FAQ

What is roof pitch?

Roof pitch is the steepness of a roof expressed as a ratio of vertical rise to horizontal run (e.g., 6:12 means 6 inches of rise per 12 inches of run). It can also be expressed in degrees or as a slope percentage.

What is the minimum roof pitch for asphalt shingles?

According to the reference chart, a 4:12 pitch (18.43°) is the minimum recommended for standard asphalt shingles. Pitches below 4:12 typically require specialized low-slope roofing materials.

What does the rafter multiplier mean?

The rafter multiplier (also called pitch factor) is the number you multiply the horizontal span by to get the actual rafter length. For a 6:12 pitch, the multiplier is 1.1180.

Is the Roof Pitch Calculator free?

Yes, the tool is completely free to use on RoofAngler.com with no registration or payment required.