Roof Pitch Calculator
Calculate roof pitch ratio, angle in degrees, and slope percentage from rise and run measurements or from an angle. Use the reference table below for all standard pitches.
Roof Pitch Calculator
Roof Pitch Reference Table
All standard roof pitches from 1/12 to 12/12, with angle in degrees, slope percentage, and classification. The pitch ratio is dimensionless — in metric countries, rise and run are measured in cm instead of inches but the ratio (and therefore the angle and slope %) is identical. Example: 6/12 US pitch = 15 cm rise per 30 cm run = 26.57°.
| Pitch | Angle (°) | Slope (%) | Type |
|---|---|---|---|
| 1/12 | 4.76° | 8.33% | Flat |
| 2/12 | 9.46° | 16.67% | Flat |
| 3/12 | 14.04° | 25.00% | Low slope |
| 4/12 | 18.43° | 33.33% | Low slope |
| 5/12 | 22.62° | 41.67% | Medium slope |
| 6/12 | 26.57° | 50.00% | Medium slope |
| 7/12 | 30.26° | 58.33% | Medium slope |
| 8/12 | 33.69° | 66.67% | Medium slope |
| 9/12 | 36.87° | 75.00% | Steep |
| 10/12 | 39.81° | 83.33% | Steep |
| 11/12 | 42.51° | 91.67% | Steep |
| 12/12 | 45.00° | 100.00% | Steep |
How to Measure Roof Pitch
- Place a level horizontally against the roof surface or a rafter in the attic. Mark 12 inches from one end.
- Measure vertically from the 12-inch mark straight down (or up) to the roof surface. This measurement is the rise.
- Express as a ratio: rise / 12. For example, if the rise is 6 inches, the pitch is 6/12.
- Convert to degrees: use this calculator or the formula: angle = atan(rise / run) × 180 / π.
Tip: You can also measure from inside the attic by holding a level against a rafter — this avoids climbing onto the roof.
Roof Pitch and Roofing Materials
| Pitch Range | Suitable Materials |
|---|---|
| 0/12 – 2/12 (Flat) | Built-up roofing (BUR), EPDM membrane, TPO, modified bitumen |
| 2/12 – 4/12 (Low slope) | Metal panels, low-slope shingles (with double underlayment) |
| 4/12 – 8/12 (Medium) | Asphalt shingles, metal panels, wood shakes, composite |
| 9/12+ (Steep) | Slate, clay/concrete tiles, cedar shakes, architectural shingles |
Frequently Asked Questions
What is the most common roof pitch?
The most common roof pitches for residential homes are 4/12 through 9/12. A 6/12 pitch (26.57°) is particularly popular because it provides good water drainage, allows easy walking for maintenance, and looks proportional on most house styles.
What roof pitch is considered steep?
A roof pitch of 9/12 (36.87°) or greater is generally considered steep. Pitches above 12/12 (45°) are classified as very steep and typically require special safety equipment for installation and maintenance.
What is the minimum roof pitch for asphalt shingles?
The minimum roof pitch for standard asphalt shingles is 4/12 (18.43°). For pitches between 2/12 and 4/12, special low-slope application methods with double underlayment are required. Below 2/12, shingles should not be used — a membrane or built-up roof system is recommended instead.
Related Calculators
- Roof Area Calculator — calculate total roof area from pitch and footprint
- Rafter Length Calculator — find rafter length from span and pitch
- Shingle Calculator — estimate shingles and bundles needed
- Board Foot Calculator — lumber for the rafters
- Slope (Degrees ↔ Percent) — convert pitch ratios to slope angles
- All Construction Calculators
Pitch calculations based on standard trigonometric formulas. Grade descriptions follow common roofing industry classifications (ICC/IBC building codes). Standard run is 12 inches (1 foot). All results are rounded for practical use.