Roof Pitch Calculator — Convert Rise/Run, Degrees & Rafter Length
Enter rise and run to instantly get roof pitch as X:12, degrees, percent, and rafter length. This calculator solves all roof pitch conversion needs in one tool.
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Common Roof Pitches
| Pitch (x:12) | Degrees | Percent | Action |
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How to Measure Roof Pitch
Measure vertically (rise) from the top plate to the peak and horizontally (run) for 12 inches of run; use attic or ladder method.
Method 1: Attic Measurement
If you have access to the attic, this is the safest method:
- Locate the roof’s ridge (peak) inside the attic
- Measure 12 inches horizontally from the ridge along the roof sheathing
- Measure vertically from that point down to the attic floor or ceiling joist
- The vertical measurement is the rise for a 12-inch run
Method 2: Exterior Measurement
If attic access isn’t available, measure from the exterior:
- Use a ladder with proper stabilization and safety precautions
- Place a level horizontally against the roof surface
- Adjust the level until it’s perfectly horizontal (bubble centered)
- Measure 12 inches from the end of the level along the roof surface
- Measure vertically from that point down to the roof surface
- This vertical measurement is the rise for a 12-inch run
Safety Note: Always use proper fall protection when working on ladders or roofs. Consider hiring a professional for steep or high roofs.
Frequently Asked Questions
Divide rise by run, then use degrees = atan(rise/run) * 180/π. Example: 6:12 → rise/run = 0.5 → degrees ≈ 26.565°.
A 6/12 pitch (26.565°) is considered a moderately steep roof. It’s walkable with proper safety equipment but steep enough to shed water and snow effectively.
Use a ladder with proper stabilization, have a spotter, wear non-slip shoes, and use a level and tape measure. For attic measurements, ensure the floor is secure and use adequate lighting.
In residential construction, 4/12 to 6/12 pitches are most common, balancing aesthetics, water drainage, and material requirements.
Steeper roofs require more roofing materials per square foot of floor area. A pitch multiplier (calculated from rafter length) helps estimate material requirements accurately.
Most asphalt shingles require at least a 2:12 pitch (about 9.5°) for proper water drainage. Lower pitches may require specialized roofing materials.
Understanding Roof Pitch Calculations
Roof pitch is a critical measurement in construction that describes the steepness of a roof. It’s typically expressed as a ratio of vertical rise to horizontal run (like 6:12), but can also be represented as an angle in degrees or a percentage grade.
Why Roof Pitch Matters
The pitch of your roof affects several important factors:
- Water drainage: Steeper pitches shed water more effectively
- Snow load: Steeper roofs allow snow to slide off more easily
- Material requirements: Steeper roofs require more materials
- Attic space: Steeper pitches create more usable attic space
- Aesthetics: Pitch affects the overall look of your home
Roof Pitch Categories
Roof pitches are generally categorized as:
- Flat roofs: 0:12 to 2:12 (0° to 9.5°)
- Low-slope roofs: 2:12 to 4:12 (9.5° to 18.4°)
- Conventional roofs: 4:12 to 9:12 (18.4° to 36.9°)
- Steep roofs: 9:12 to 20:12 (36.9° to 59°)
- Very steep roofs: Over 20:12 (over 59°)
For more information on building codes and roof construction standards, consult the International Code Council or your local building department.