Free technical tool
Roof pitch calculator
Convert measurements, degrees, percent, and rise per 12. Then review what the result means for an IKO asphalt shingle installation.
Enter what you already know
The unit does not change pitch as long as rise and horizontal run use the same one.
How it is calculated
Pitch is rise divided by horizontal run. Percent multiplies that ratio by 100; angle uses the arctangent function, and x:12 normalizes the run to twelve units.
Equivalent result
Every conversion updates from the same roof pitch.
- Ratio
- 4:12
- Percent
- 33.3%
- Angle
- 18.4°
- Pitch factor
- 1.054
Multiply a horizontal length or area by this factor to estimate its sloped measurement.
Geometric pitch reading
12 run
IKO asphalt shingle interpretation
Conventional slope
At 4:12 and above, the roof is in the conventional range. Still confirm the product sheet, roof deck, and project conditions.
Measure from a safe location
Do not climb onto a roof only to obtain these measurements. Use plans, measure from an accessible underside, or ask trained personnel with fall protection for help.
Methodology and sources
Sources reviewed July 22, 2026 UTC.
Continue your project
Review measurement, installation, products, and decisions where pitch changes the roofing system.
View every technical roof pitch resource
Frequently asked questions
Are pitch and angle the same thing?
They describe the same incline in different formats. Pitch is commonly shown as percent or rise per 12; angle is shown in degrees.
Can I mix centimeters and meters?
Convert both measurements to the same unit before calculating. The final ratio has no unit.
Does this result approve an installation?
No. It is a mathematical conversion with general IKO guidance. Product instructions, applicable code, and professional review take precedence.