Roof pitch calculator
Work out roof pitch, angle and rafter length factor from a measured rise and run.
Roof pitch calculator
Work out roof pitch, angle and rafter length factor from a measured rise and run.
Enter the rise and run to see the roof pitch.
Roof pitch
Project summary
How it works
Steepness and pitch descriptions here are general, not building code requirements. Roofing material, ventilation and structural requirements vary by jurisdiction; check local code before building.
Roof pitch calculator
Measuring rise and run
Pitch is measured as vertical rise over a horizontal run, conventionally normalized to a 12 inch run: a roof that climbs 6 inches for every 12 inches it runs is a "6 in 12" pitch. You can measure this directly with a level and tape along a rafter or gable end, holding the level perfectly horizontal for the run measurement.
Why the rafter factor matters
The rafter length factor converts a flat, horizontal measurement into the actual sloped length material has to cover. A steeper roof needs proportionally more rafter, decking and roofing material than its footprint alone suggests, which is exactly what the roof square footage and shingle calculators use this same pitch for.
Frequently asked questions
What does a 6 in 12 roof pitch mean?
A 6 in 12 pitch means the roof rises 6 inches for every 12 horizontal inches of run, which works out to about a 26.6 degree angle and a 50 percent grade. Enter your own rise and run above to check a different pitch.
How do I measure my roof pitch?
Hold a level horizontally against the underside of a rafter or against the roof surface, mark 12 inches along the level from the roof, then measure the vertical distance down to the roof surface at that mark. That vertical measurement, in inches, is your rise per 12 inches of run.
What is a 4 in 12 roof pitch?
A 4 in 12 pitch means the roof rises 4 inches for every 12 inches of horizontal run. It is the lowest pitch commonly used for residential shingled roofs. Steeper pitches shed water and snow better but cost more to build. The calculator converts your rise and run into pitch, slope angle and roof area.
What is the steepest roof pitch allowed?
Most building codes do not set a maximum pitch, but very steep roofs above 12 in 12 require special framing and are difficult to walk. Some HOAs or historical districts limit pitch in the other direction, requiring a minimum pitch for aesthetic reasons. The calculator works with any pitch you enter.
How do I measure roof pitch from the ground?
Stand level with the eave and measure 12 feet horizontally from the wall. Then measure the vertical rise to the roof edge at that point. The rise in inches equals the pitch. For example, a 4 foot rise over 12 feet of run is a 4 in 12 pitch. The calculator accepts rise and run measurements in any unit.
Does roof pitch affect shingle cost?
Steeper roofs waste more shingles because of the angle, so the waste factor increases with pitch. A 12 in 12 pitch might need 40 percent waste versus 10 percent for a 4 in 12 pitch. Labour costs also rise on steep roofs. The calculator adjusts material quantities based on your pitch and waste factor.
Can I walk on a steep roof?
Pitches above 6 in 12 are difficult and dangerous to walk without special equipment. Pitches above 10 in 12 require roof brackets or a safety harness. For steep roofs, hire a professional roofer. The calculator helps you estimate materials so you can get accurate bids from roofers.
What is the minimum roof pitch for shingles?
Most shingle manufacturers require a minimum pitch of 2 in 12. Below that, water does not shed fast enough and leaks develop. For very low slopes, modified bitumen or single ply membranes are used instead. The calculator shows you the pitch you entered and flags if it is below common minimums.