Calculate roof pitch in degrees and percentage from ridge height and span. The tool checks which roofing materials fit your angle and computes rafter length and ridge height for any building width.
Roof Pitch Calculator - Degrees, Percentage and Material Compatibility
Calculate roof pitch in degrees and percentage from ridge height and span. The tool checks which roofing materials fit your angle and computes rafter length and ridge height for any building width.
Parameters
Enter data for calculations
💡 Fill in all required fields to unlock the calculate button
Roof pitch, slope and rafter length - one calculation
Three modes in one tool. Enter ridge height and half-span to get the pitch angle, or convert between degrees and percentage. The calculator also matches your pitch against 9 roofing material types and flags which ones are compatible. If you enter the full building width, it computes ridge height and rafter length for the actual structure.
How to use the roof pitch calculator - step by step
- Choose calculation mode - pitch from dimensions, degrees-to-percentage, or percentage-to-degrees.
- Ridge height above wall - vertical distance from wall plate to ridge peak in meters. Measure inside the attic or read from the architectural drawing.
- Half-span - horizontal distance from the outside wall to the ridge. For a symmetric gable roof, this equals half the building width.
- Roof type (optional) - gable, mono-pitch, hip or mansard. Adds a recommended pitch range for context.
- Full building width (optional) - enter the total width to compute the actual ridge height and rafter length at the calculated pitch.
- Read the results - pitch in degrees and percentage, material compatibility list, ridge height and rafter length.
Roofing material compatibility by pitch angle
Each roofing material has a minimum and maximum pitch. Install a material outside its range and water ingress, wind damage or warranty voidance can follow.
| Material | Min (deg) | Max (deg) | Optimal range |
|---|---|---|---|
| Torch-on felt (bitumen) | 3 | 25 | 5-15 deg |
| Metal tile (steel) | 9 | 60 | 15-45 deg |
| Standing seam metal | 10 | 75 | 15-45 deg |
| Asphalt shingles | 10 | 85 | 15-45 deg |
| Clay tiles (ceramic) | 20 | 60 | 30-45 deg |
| Concrete tiles | 22 | 60 | 30-45 deg |
| Beaver-tail tiles | 25 | 65 | 35-50 deg |
| Natural slate | 30 | 90 | 35-55 deg |
| Thatch / reed | 30 | 60 | 40-55 deg |
Degrees vs percentage - conversion reference
The percentage slope is the tangent of the angle multiplied by 100. A 45-degree pitch equals exactly 100% slope (1:1 rise-to-run). Common reference values:
| Degrees | Percentage | Rise per 12 in run | Typical use |
|---|---|---|---|
| 5 | 8.7% | 1/12 | Flat roofs, carports |
| 15 | 26.8% | 3.2/12 | Low-slope metal roofing |
| 30 | 57.7% | 6.9/12 | Standard gable roofs |
| 45 | 100.0% | 12/12 | Steep gable, heavy snowfall areas |
| 60 | 173.2% | 20.8/12 | Mansard lower slopes, slate |
Practical examples
Result: 35.0 deg pitch, 70.0% slope, rafter length 6.10 m
Result: 14.0 deg pitch, 25.0% slope - metal sheeting or asphalt shingles only
Result: 70.0% slope
Result: 45.0 deg - steep but common in alpine regions
Result: ridge height 2.9 m, rafter length 5.8 m
FAQ - Frequently asked questions
Related tools
Roof Calculator
Calculate roofing materials, underlayment, ridge cap and total cost for any roof shape - See calculator
Insulation Calculator
Calculate insulation thickness and R-value for walls, attics and floors - See calculator
Concrete Calculator
Calculate concrete volume, bags and cost for slabs, footings and columns - See calculator
Rebar Calculator
Calculate reinforcement steel weight, bar count and total length for concrete elements - See calculator
Self-Leveling Screed Calculator
Calculate how many bags of self-leveling compound you need for any room - See calculator