How roof slope is calculated
The tangent of the roof angle gives the relationship between rise and run. Multiplying that ratio by 12 converts it to common roofing pitch notation.
Roof slope example
An angle of approximately 26.57 degrees corresponds to a 6:12 roof pitch and a 50% slope.
What is slope percentage?
A 50% roof slope means the roof rises 0.5 units for every 1 unit of horizontal run.
Frequently asked questions
What roof pitch is 45 degrees?
A 45-degree roof has a 12:12 pitch and a 100% slope.
What roof pitch is about 26.6 degrees?
Approximately 6:12.
What is roof slope factor?
It is the multiplier used to convert horizontal footprint area to sloped roof surface area.
Using this calculator effectively
This tool starts with a roof angle and converts it into pitch, slope percentage and slope factor. It is useful when an angle reading is available but another roof-slope format is required.
Common uses
- Converting degrees into an approximate X-in-12 pitch.
- Finding slope percentage from a measured angle.
- Getting a slope factor for roof-area estimation.
Tips for a better estimate
- Use a reliable angle measurement from the roof plane or framing.
- Avoid rounding the angle too early when precision matters.
- Treat the result as geometry only; roofing-system limits and code requirements are separate.
Helpful guides
Related calculations
Roof Pitch Calculator · Roof Square Footage Calculator · Roof Shingle Calculator