Roof Pitch Calculator
Calculate roof pitch, angle, rafter length, and slope from rise and run measurements
Calculate Roof Pitch
Measurements
Vertical distance from roof edge to peak
Horizontal distance from wall to roof center
Roof Pitch Results
Please Complete Required Fields
- ⚠️Please enter both rise and run values
Roof Measurements
Roof Classification
Safety Assessment
Formulas used:
Rafter Length: √(rise² + run²) (Pythagorean theorem)
Pitch Percentage: (rise / run) × 100
Pitch Angle: arctan(rise / run)
Pitch Ratio: (rise / run) × 12
Example Calculation
Standard Residential Roof
Rise: 1.5m (4.9 feet)
Run: 6m (19.7 feet)
Building Length: 12m total (6m from center to wall)
Calculation Steps
1. Rafter Length = √(1.5² + 6²) = √(2.25 + 36) = √38.25 = 6.18m
2. Pitch Percentage = (1.5 / 6) × 100 = 25%
3. Pitch Angle = arctan(1.5 / 6) = arctan(0.25) = 14°
4. Pitch Ratio = 0.25 × 12 = 3:12
5. Roof Multiplier = √(0.25² + 1) = √1.0625 = 1.031
Result: 3:12 pitch, 25% slope, 14° angle
Roof Pitch Guide
Flat Roof
0.5:12 to 2:12 (4-16%)
Requires special drainage
Low Pitch
2:12 to 4:12 (16-33%)
Difficult to maintain
Conventional
4:12 to 9:12 (33-75%)
Easiest to construct
High Pitch
9:12+ (75%+)
Requires extra fasteners
Measurement Tips
Measure rise from the roof deck to the ridge
Run is horizontal distance from wall to roof center
Use a speed square for quick angle measurements
Check local building codes for minimum pitch requirements
Consider climate: steeper for snow, lower for wind
Safety First: Always use proper safety equipment when working on roofs.
Understanding Roof Pitch
What is Roof Pitch?
Roof pitch is the slope of a roof expressed as a ratio, percentage, or angle. It's typically shown as rise over run (how many inches the roof rises vertically for every 12 inches of horizontal distance).
Why Roof Pitch Matters
- •Water Drainage: Steeper pitches shed water faster
- •Snow Load: Steep roofs shed snow more effectively
- •Material Choice: Different pitches require different materials
- •Attic Space: Higher pitches provide more usable space
Calculation Methods
Pythagorean Theorem:
rafter² = rise² + run²
Pitch Calculation:
pitch = rise / run
Angle Conversion:
angle = arctan(pitch)
X:12 Ratio:
x = pitch × 12
Pro Tip: A 6:12 pitch means the roof rises 6 inches for every 12 inches of horizontal distance, creating a 26.57° angle.
Common Applications
Residential
Most homes use 4:12 to 9:12 pitches for optimal balance of aesthetics, functionality, and construction efficiency.
Commercial
Often use lower pitches (1:12 to 4:12) for cost efficiency and easier maintenance access.
Specialty
Gothic, Victorian, and other architectural styles may use very steep pitches (12:12 or higher) for aesthetic purposes.