Roof Pitch Calculator
Pitch, angle, grade and the slope factor — from rise and run, rise and span, rise per 12, an angle or a grade.
Pitch
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Roof Pitch · Result
CalculatedPITCH
6:12 pitch
- Rise per 12
- 6.00
- Angle
- 26.57°
- Grade
- 50%
- Slope factor
- 1.1180
- Hip / valley factor
- 1.5000
Code references & assumptions · 1
How this result is supported
- ASSUMPTIONThe pitch text rounds the rise to the nearest 1/8 per 12 for trade notation — at most 1/16 per 12 from the exact value, which is the rise per 12 reported beside it
- ASSUMPTION
What do these evidence labels mean?
- PRIMARY-VERIFIED
- directly supported by one authoritative primary source, quoted with section/page/figure
- CROSS-VERIFIED
- independently supported by two or more appropriate authoritative sources
- DERIVED
- mathematically derived from PRIMARY-VERIFIED values; the derivation is preserved in data and in code
- INTERPRETED
- a source exists but translating it into calculator behaviour required interpretation
- CONVENTION
- recognised trade practice, not a mandatory provision
- ASSUMPTION
- product/design assumption or useful default with no authoritative basis
- UNVERIFIED
- insufficient authoritative evidence
Code references and product data are quoted in the units their source uses.
Reference checks are informational, not compliance determinations.
How roof pitch is calculated
Pitch, angle and grade are three ways of saying the same thing, and a roof is usually described in whichever one the person measuring had to hand. Enter any of them and the calculator returns the others, along with the framing-square setting the number rounds to.
The slope factor is the one that does the work elsewhere: multiply a plan area by it and you get the sloped area. A 6:12 roof has a slope factor of about 1.118, so a 1,000 ft² footprint is roughly 1,118 ft² of roof.
The hip and valley factor is a different number and is not interchangeable with it. It converts a plan run into the length of a hip or valley rafter, which runs diagonally across two slopes rather than up one.
slope factor = √(rise² + 12²) ÷ 12
What plan area is multiplied by.
angle = arctan(rise ÷ 12)
grade % = rise ÷ 12 × 100