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.
What is a 25 degree roof pitch in percent?
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.
A pitch of 25 degrees and a percentage slope describe the same roof, but the two units rarely appear side by side. Architects and structural drawings favour degrees, while manufacturer datasheets and installation guides usually state a minimum slope in percent. The conversion runs through the tangent of the angle multiplied by one hundred, so it is not linear: doubling the angle does not double the slope. For 25 degrees this page returns the slope as a percentage, sorts the roof into a pitch category, and lists which coverings stay inside the manufacturer range at that angle and which fall outside it. You can also reverse the conversion or derive the pitch straight from ridge height and span.
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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
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Calculator verified by the LiczGrupa.pl team
Content, formulas and results have been reviewed for accuracy and relevance by our team of specialists.
Reviewed by: Patryk Matyjasik