Roof Pitch Calculator
A clear view of your roof’s slope.
Convert rise, run, pitch and degrees.
Your measurements
Local calculationYour roof pitch
Live resultrise per 12 units of horizontal run
Enter valid measurements to see your result.
Geometry estimates only. This tool does not assess structural safety or building-code compliance.
A slope, three ways to read it.
Roof pitch describes how much a roof rises over a horizontal distance. A 6:12 pitch rises 6 units for every 12 units of run. The same slope is 26.57° or 50.00%.
- Rise
- The vertical height from the horizontal baseline to the roof’s upper point.
- Run
- The horizontal distance covered by that slope. It is not the length along the roof.
- Span
- The full horizontal width. On a symmetrical gable roof, each side’s run is half the span. This calculator does not divide your input by two.
Try it with familiar numbers.
A 6-inch rise over a 12-inch run
6 ÷ 12 = 0.5. Multiply by 12 for a 6:12 pitch, or by 100 for a 50% slope. The arctangent of 0.5 gives 26.57°.
A roof angle of 30 degrees
tan(30°) ≈ 0.57735. That gives a 6.93:12 pitch and a 57.74% slope. An angle of 30° is not a 30% slope.
The calculation, explained.
Let r be rise divided by horizontal run, with both lengths in the same unit.
Pitch per 1212 × r
Angle in degreesatan(r) × 180 / π
Slope percent100 × r
Ratio from an angletan(angle × π / 180)
Calculations use unrounded numbers internally; results display two decimal places. Positive results that would round to zero display <0.01. Angles that would round to 90° display >89.99°.
A few useful answers.
Is roof pitch the same as roof angle?
They describe the same slope in different ways. Pitch uses rise per 12 units of run; an angle uses degrees. A 12:12 pitch is 45°, while a 6:12 pitch is about 26.57°.
Can I use meters or centimeters?
Yes. Use the same unit for rise and run. Switching the unit converts both lengths, so the actual dimensions and roof pitch stay the same. For example, 0.15 m over 0.30 m becomes 15 cm over 30 cm.
Should I enter the full roof span?
No. Enter the horizontal run of the slope you are measuring. For a symmetrical gable roof only, the run is half the full span. Roof shape matters, so this tool does not infer the run from a span.
Can the rise or angle be zero?
Yes. Zero rise or a zero-degree angle represents a horizontal line, giving zero pitch and zero slope. Run must be greater than zero, and an angle must be less than 90°.
Why are my results rounded?
Two decimal places keep results easy to read. Internal calculations keep their precision. The copied result matches the displayed rounding, including the <0.01 and >89.99° boundary labels.
Does this tell me if my roof is safe?
No. These are geometric conversions. Material requirements, drainage, loading and local building codes need appropriate professional assessment.
Method & privacy
This calculator uses right-triangle trigonometry and exact unit definitions: 1 inch = 0.0254 m, 1 foot = 0.3048 m, and 1 cm = 0.01 m. Reference: NIST’s SI conversion factors.
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