Roof Pitch Calculator
Enter rise and run (or any two values) to instantly convert roof pitch between x/12 ratio, degrees, percentage slope, and pitch multiplier.
Enter Any One Value
:12
°
%
Pitch
6.00:12
Moderate Slope
Degrees26.57°
Percent (%)50.0%
Pitch Multiplier1.1180×
Rafter / Ft of Run1.1180 ft
Plumb Cut Angle26.6°
Seat Cut Angle63.4°
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Standard Pitch Reference
| Pitch | Degrees | Percent | Multiplier | Rafter/ft |
|---|---|---|---|---|
| 3:12 | 14.0° | 25.0% | 1.031 | 1.031 ft |
| 4:12 | 18.4° | 33.3% | 1.054 | 1.054 ft |
| 5:12 | 22.6° | 41.7% | 1.083 | 1.083 ft |
| 6:12 | 26.6° | 50.0% | 1.118 | 1.118 ft |
| 7:12 | 30.3° | 58.3% | 1.158 | 1.158 ft |
| 8:12 | 33.7° | 66.7% | 1.202 | 1.202 ft |
| 9:12 | 36.9° | 75.0% | 1.250 | 1.250 ft |
| 10:12 | 39.8° | 83.3% | 1.302 | 1.302 ft |
| 12:12 | 45.0° | 100.0% | 1.414 | 1.414 ft |
How to Use This Calculator
Enter any two values and the calculator converts to all other formats automatically:
- Rise — The vertical height your roof gains, typically measured in inches over a 12-inch horizontal run
- Run — The horizontal distance, almost always 12 inches for standard pitch notation
- Degrees — The angle of the roof slope from horizontal (0° = flat, 45° = 12/12 pitch)
- Percent slope — Rise divided by run, expressed as a percentage (useful for drainage design)
The calculator also outputs the pitch multiplier — the factor you multiply your footprint area by to get actual roof area. Use this with the Roof Area Calculator.
The Formula
Pitch Ratio = Rise : 12 (e.g., 6:12)
Degrees = arctan(Rise / Run) × (180 / π)
Percent Slope = (Rise / Run) × 100
Pitch Multiplier = √(Run² + Rise²) / Run
For a 6/12 pitch:
Degrees = arctan(6/12) = 26.57°
Percent = (6/12) × 100 = 50%
Multiplier = √(144 + 36) / 12 = √180 / 12 = 1.118
Degrees = arctan(Rise / Run) × (180 / π)
Percent Slope = (Rise / Run) × 100
Pitch Multiplier = √(Run² + Rise²) / Run
For a 6/12 pitch:
Degrees = arctan(6/12) = 26.57°
Percent = (6/12) × 100 = 50%
Multiplier = √(144 + 36) / 12 = √180 / 12 = 1.118
Example: Converting a 7/12 Pitch
Example: 7/12 Roof Pitch Conversion
Input Pitch7/12
Rise7 inches per 12 inches run
Degreesarctan(7/12) = 30.26°
Percent Slope58.3%
Pitch Multiplier1.158
ClassificationSteep slope (requires safety harness)
A 7/12 pitch adds 15.8% more area compared to the footprint. A 30×40 ft house with this pitch has 1,200 × 1.158 = 1,390 sq ft of roof area.
Roof Pitch Quick Reference
| Pitch | Degrees | % Slope | Multiplier | Category |
|---|---|---|---|---|
| 1/12 | 4.8° | 8.3% | 1.003 | Flat |
| 2/12 | 9.5° | 16.7% | 1.014 | Low slope |
| 3/12 | 14.0° | 25% | 1.031 | Low slope |
| 4/12 | 18.4° | 33.3% | 1.054 | Moderate |
| 5/12 | 22.6° | 41.7% | 1.083 | Moderate |
| 6/12 | 26.6° | 50% | 1.118 | Moderate |
| 7/12 | 30.3° | 58.3% | 1.158 | Steep |
| 8/12 | 33.7° | 66.7% | 1.202 | Steep |
| 9/12 | 36.9° | 75% | 1.250 | Steep |
| 12/12 | 45.0° | 100% | 1.414 | Very steep |
Frequently Asked Questions
Roof pitch is the measure of a roof's steepness expressed as rise over 12 inches of run. A 6/12 pitch rises 6 inches for every 12 horizontal inches. It can also be expressed in degrees (26.6°) or as a percentage (50%).
Hold a level horizontally against a rafter. Mark 12 inches along the rafter from the wall. Measure vertically from the 12-inch mark down to the level. That vertical measurement is your rise. So if it's 5 inches, you have a 5/12 pitch.
Asphalt shingles require a minimum 2/12 pitch (with extra underlayment) or 4/12 for standard installation. Standing seam metal can be installed at 1/2:12 or flatter. Tile requires 2.5/12 minimum. Check your manufacturer's specifications for exact minimums.
Degrees = arctan(Rise/Run). For 6/12: arctan(0.5) = 26.57°. You can use a scientific calculator or this tool to do the conversion instantly.
Pitches up to 6/12 can typically be walked without special equipment on dry surfaces. At 7/12 and above, most professionals use safety harnesses. At 9/12 and steeper, scaffolding or roof jacks are strongly recommended.