What Is Roof Pitch?
Roof pitch is the steepness or angle of your roof. It’s expressed as the ratio of vertical rise to horizontal run. For example, a 6/12 pitch means the roof rises 6 inches for every 12 inches of horizontal distance.
Understanding pitch is crucial for:
- Choosing appropriate roofing materials
- Calculating material quantities
- Estimating labor costs
- Planning drainage and snow load
How Roof Pitch Is Expressed
Standard Notation (X/12)
The most common method in the US:
| Notation | Meaning | Angle |
|---|---|---|
| 4/12 | Rises 4” per 12” run | 18.4° |
| 6/12 | Rises 6” per 12” run | 26.6° |
| 8/12 | Rises 8” per 12” run | 33.7° |
| 12/12 | Rises 12” per 12” run | 45° |
Degrees
Architects and engineers often use degrees:
- Low slope: 0° to 18.4° (less than 4/12)
- Conventional: 18.4° to 45° (4/12 to 12/12)
- Steep: Above 45° (greater than 12/12)
Percentage
Sometimes expressed as a percentage:
- 4/12 = 33.3%
- 6/12 = 50%
- 12/12 = 100%
How to Measure Roof Pitch
Method 1: From the Attic (Safest)
- Place a level horizontally against a rafter
- Mark 12 inches from the end touching the rafter
- Measure vertically from the 12-inch mark to the rafter
- That measurement is your pitch (e.g., 6 inches = 6/12 pitch)
Method 2: From the Roof
- Place a level on the roof surface
- Mark 12 inches from one end
- Measure down from level to roof at the 12-inch mark
- That measurement is your pitch
Method 3: Using a Pitch Finder Tool
- Place the tool on the roof or rafter
- Read the pitch directly from the gauge
- Most accurate method for quick measurements
Safety note: If measuring from the roof, use proper fall protection and work with a helper.
Roof Pitch Categories
Low-Slope Roofs (Below 3/12)
Characteristics:
- Nearly flat appearance
- Requires special roofing systems
- Common on commercial buildings
Suitable materials:
- Built-up roofing (BUR)
- Modified bitumen
- EPDM rubber
- TPO/PVC membranes
Minimum pitch for shingles: 2/12 with special underlayment
Conventional Slope (4/12 to 9/12)
Characteristics:
- Most residential roofs
- Good water shedding
- Easy to walk on (4/12 to 6/12)
Suitable materials:
- Asphalt shingles
- Wood shakes
- Metal panels
- Clay/concrete tiles
Steep Slope (9/12 and Above)
Characteristics:
- Dramatic appearance
- Excellent water shedding
- Difficult to work on
- Higher material and labor costs
Suitable materials:
- All conventional materials
- Slate (often requires steep pitch)
- Some specialty shingles
Pitch and Roofing Material Selection
| Material | Minimum Pitch | Maximum Pitch |
|---|---|---|
| Asphalt shingles | 2/12* | No limit |
| Metal panels | 3/12 | No limit |
| Wood shakes | 4/12 | No limit |
| Clay tiles | 4/12 | No limit |
| Slate | 4/12 | No limit |
| Built-up roofing | 1/4/12 | 3/12 |
| EPDM/TPO | 1/4/12 | Any |
*2/12 requires double underlayment and special application
Calculating Roof Area from Pitch
Roof pitch directly affects the actual surface area of your roof.
Pitch Factor (Multiplier)
| Pitch | Factor |
|---|---|
| 3/12 | 1.031 |
| 4/12 | 1.054 |
| 5/12 | 1.083 |
| 6/12 | 1.118 |
| 7/12 | 1.158 |
| 8/12 | 1.202 |
| 9/12 | 1.250 |
| 10/12 | 1.302 |
| 12/12 | 1.414 |
Formula
Roof Area = Footprint Area × Pitch Factor
Example:
- House footprint: 1,500 sq ft
- Roof pitch: 6/12
- Roof area: 1,500 × 1.118 = 1,677 sq ft
Use our Roofing Calculator for automatic calculations.
Pitch and Labor Costs
Steeper roofs cost more to install due to:
- Safety equipment requirements
- Slower work pace
- Specialized techniques
Typical Labor Multipliers
| Pitch | Labor Factor |
|---|---|
| 4/12 to 6/12 | 1.0× (base rate) |
| 7/12 to 9/12 | 1.15× to 1.25× |
| 10/12 to 12/12 | 1.25× to 1.50× |
| Above 12/12 | 1.50× to 2.00× |
Pitch and Weather Performance
Snow Load
- Low pitch: Snow accumulates, requires stronger structure
- 4/12 to 6/12: Snow may slide or stay depending on conditions
- Above 8/12: Snow slides off more readily
Snow country recommendation: Minimum 6/12 pitch
Rain and Water
- Low pitch: Slower drainage, higher leak risk
- Higher pitch: Better water shedding
- Any pitch: Proper underlayment and flashing critical
Wind Resistance
- Low pitch: Less wind uplift on surface
- Steep pitch: More wind resistance, higher uplift risk at eaves
- Optimal: 4/12 to 6/12 for most wind zones
Common Pitch Mistakes
| Mistake | Problem | Solution |
|---|---|---|
| Wrong shingles on low pitch | Leaks, warranty void | Use appropriate low-slope materials |
| Mismatched additions | Poor drainage, ice dams | Match existing pitch or design proper transitions |
| Ignoring pitch for estimates | Under-ordering materials | Always use pitch factor in calculations |
| Not accounting for walkability | Safety hazards | Plan for appropriate equipment on steep roofs |
Converting Pitch to Degrees
Formula
Angle (degrees) = arctan(rise/12) × (180/π)
Quick Reference
| Pitch | Degrees |
|---|---|
| 1/12 | 4.8° |
| 2/12 | 9.5° |
| 3/12 | 14.0° |
| 4/12 | 18.4° |
| 5/12 | 22.6° |
| 6/12 | 26.6° |
| 7/12 | 30.3° |
| 8/12 | 33.7° |
| 9/12 | 36.9° |
| 10/12 | 39.8° |
| 11/12 | 42.5° |
| 12/12 | 45.0° |
Pitch and Home Design
Curb Appeal
- Low pitch (2-4/12): Modern, contemporary look
- Medium pitch (5-7/12): Traditional, versatile
- Steep pitch (8-12/12): Dramatic, classic, or Victorian style
Attic Space
- Low pitch: Minimal attic, crawl space only
- 6/12 and above: Usable attic storage
- 9/12 and above: Potential living space
Building Codes
Most codes require:
- Minimum 1/4”/foot slope for drainage
- Fire-rated assemblies for certain pitches
- Specific underlayment based on pitch
Always check local building codes before starting a roofing project.
Calculate Your Roof
Ready to plan your roofing project? Use our free calculators:
- Roofing Calculator - Material and cost estimates
- Rafter Calculator - Rafter lengths and cuts
Pro Tip: When in doubt about your roof pitch, hire a professional to measure. An incorrect pitch measurement can lead to ordering the wrong materials or using incompatible roofing systems. Many roofing contractors will provide a free estimate that includes accurate pitch measurements.