When to use this calculator
Find a roof angle from its vertical rise and horizontal run. Run is horizontal distance, not the sloped roof length.
Explore the slopes, layouts & dimensions calculators for other questions in this topic. For a related calculation, use the Stair Riser Calculator: Find equal riser height from total rise and chosen number of risers.
PUTTING IT INTO PRACTICE
Roof Pitch: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| Rise | 3 |
| Horizontal run | 6 |
| Result | 26.565051 degrees |
- Check the input labels and enter the example values above.
- Apply the relationship: Angle = atan(rise/run) × 180/π.
- The result is 26.565051 degrees, rounded for display.
How to interpret your result
Run is horizontal distance, not the sloped roof length.
Use horizontal run for a slope calculation and perpendicular rise for height. A slope percentage is not an angle in degrees. These geometric tools do not establish compliance with local design or building requirements.
Frequently asked questions
Is a 10% slope the same as a 10° angle?
No. A 10% slope has a rise/run ratio of 0.10. Its angle is the arctangent of that ratio.
How do I use the roof pitch calculator?
Enter rise, horizontal run. The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Angle = atan(rise/run) × 180/π.
What should I check before using the result?
Run is horizontal distance, not the sloped roof length.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
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