Roof Pitch Calculator
Calculate roof pitch from rise and run, convert between degrees and pitch notation, find the slope factor for rafter calculations, and estimate roofing squares for your project.
Enter Roof Pitch
/12
Pitch Results
Conventional6/12
Roof Pitch
26.6°
Angle
Slope Factor (Multiplier)
Multiply footprint area by this to get actual roof area
1.118
Conversions
Rise per foot6.00"
Percent Grade50.00%
Degrees26.57°
Common pitch reference
| Pitch | Angle | Factor |
|---|---|---|
| 2/12 | 9.5° | 1.014 |
| 4/12 | 18.4° | 1.054 |
| 5/12 | 22.6° | 1.083 |
| 6/12 | 26.6° | 1.118 |
| 7/12 | 30.3° | 1.158 |
| 8/12 | 33.7° | 1.202 |
| 9/12 | 36.9° | 1.250 |
| 10/12 | 39.8° | 1.302 |
| 12/12 | 45.0° | 1.414 |
Understanding Roof Pitch
Roof pitch describes the steepness of a roof as the ratio of vertical rise to horizontal run. In the US, pitch is expressed as inches of rise per 12 inches of run (e.g., "6/12" means 6 inches rise per foot of run). This calculator converts between pitch notation, degrees, and slope factor.
Common Roof Pitches
| Pitch | Degrees | Slope Factor | Typical Use |
|---|---|---|---|
| 2/12 | 9.46° | 1.014 | Low slope, membrane roofing |
| 4/12 | 18.43° | 1.054 | Minimum for standard shingles |
| 6/12 | 26.57° | 1.118 | Common residential |
| 8/12 | 33.69° | 1.202 | Steeper residential |
| 12/12 | 45.00° | 1.414 | 45° pitch, very steep |
Calculating Roofing Squares
A roofing "square" is the industry standard unit for roof area, equal to 100 square feet. To calculate squares needed: measure the building footprint, multiply by the slope factor, and divide by 100. Add 10-15% for waste, hips, and valleys.
Frequently Asked Questions
- What is a 6/12 roof pitch?
- A 6/12 roof pitch means the roof rises 6 inches for every 12 inches of horizontal run. This is equivalent to a 26.57° angle and has a slope factor of 1.118. A 6/12 pitch is considered a conventional or medium slope, suitable for most residential roofing materials including asphalt shingles.
- How do I measure roof pitch?
- To measure roof pitch, place a level horizontally against the roof surface, mark 12 inches from one end, and measure the vertical distance from that mark down to the roof. That vertical measurement (in inches) is your pitch "over 12." For example, if you measure 6 inches, you have a 6/12 pitch.
- What is slope factor and why does it matter?
- Slope factor (also called roof multiplier) converts a roof's horizontal footprint to actual roof surface area. For example, a 6/12 pitch has a slope factor of 1.118, meaning actual roof area is 11.8% larger than the footprint. This is essential for calculating shingles, underlayment, and rafter lengths.
- How do I calculate roofing squares?
- A roofing "square" equals 100 square feet of roof area. To calculate: multiply your building footprint (length × width) by the slope factor, then divide by 100. For example, a 30' × 40' building (1,200 sq ft) with a 6/12 pitch (1.118 slope factor) = 1,342 sq ft actual roof area = 13.42 squares.
- What is the minimum roof pitch for shingles?
- Most asphalt shingle manufacturers require a minimum 4/12 pitch for standard installation. Roofs between 2/12 and 4/12 need additional underlayment and special low-slope application methods. Roofs below 2/12 are considered flat and require membrane roofing systems instead of shingles.
- How do I convert roof pitch to degrees?
- To convert pitch to degrees, use: degrees = arctan(rise/run) × (180/π). For example, a 6/12 pitch: arctan(6/12) = arctan(0.5) = 26.57°. Common conversions: 4/12 = 18.43°, 6/12 = 26.57°, 8/12 = 33.69°, 12/12 = 45°.