Roof Pitch Calculator
Calculate roof pitch, angles, rafter lengths, and material quantities for your roofing project. Supports multiple calculation methods and roof types.
Pitch Inputs
Building Dimensions (Optional)
Calculation Results
Pitch Information
Measurements
Common Roof Pitches
| Pitch Ratio | Angle | Slope % | Classification | Typical Use |
|---|---|---|---|---|
| 2/12 | 9.46° | 16.67% | Low | Flat roofs, minimal slope |
| 3/12 | 14.04° | 25% | Low | Low-pitch residential |
| 4/12 | 18.43° | 33.33% | Medium | Standard residential |
| 6/12 | 26.57° | 50% | Medium | Common residential |
| 8/12 | 33.69° | 66.67% | Medium | Steeper residential |
| 12/12 | 45° | 100% | Steep | Very steep, architectural |
Roof Types
Gable Roof
The most common roof type with two sloping sides that meet at a ridge. Simple construction, good drainage, and cost-effective.
Hip Roof
All four sides slope downward to the walls. More stable and resistant to wind, but more complex construction with hip rafters.
Shed Roof
Single sloping surface, simplest roof type. Common for additions, porches, and modern architecture.
Gambrel Roof
Two slopes on each side with the lower slope steeper. Classic barn style, provides more attic space.
Mansard Roof
Four-sided roof with two slopes on each side. French style, maximizes living space in the attic.
Dutch Gable
Combination of gable and hip roof. Combines the benefits of both styles with added visual interest.
Flat Roof
Minimal slope (typically 1-2°) for drainage. Common in commercial buildings and modern residential design.
Calculation Methods
Rise and Run
The most common method. Enter the vertical rise (in inches) and horizontal run (typically 12 inches for standard pitch notation). The calculator will determine the pitch ratio (e.g., 6/12), angle, and percentage slope.
Pitch = (Rise ÷ Run) × 12
Angle (Degrees)
Enter the roof angle in degrees. The calculator will convert this to pitch ratio, rise/run, and percentage slope.
Rafter Length and Run
If you know the rafter length and horizontal run, enter both values. The calculator uses the Pythagorean theorem to find the rise and calculate pitch.
Rafter² = Rise² + Run²
Percentage Slope
Enter the slope as a percentage (e.g., 50% for a 6/12 pitch). The calculator converts this to pitch ratio, angle, and rise/run.
Frequently Asked Questions
Roof pitch is the angle or slope of a roof, typically expressed as a ratio of vertical rise to horizontal run (e.g., 6/12 means 6 inches of rise for every 12 inches of run). It can also be expressed as an angle in degrees or a percentage slope.
You can measure roof pitch by finding the vertical rise over a 12-inch horizontal run. Use a level and tape measure, or use a pitch gauge tool. Alternatively, measure the rafter length and horizontal run, or use an angle finder to measure the roof angle directly.
For areas with heavy snow, steeper pitches (6/12 to 12/12) help shed snow. For high wind areas, moderate pitches (4/12 to 6/12) are often better. For areas with minimal precipitation, lower pitches (2/12 to 4/12) work well. Always consult local building codes.
Typically, 3 bundles of shingles cover 1 square (100 square feet) of roof area. The calculator accounts for waste factor (default 10%) to ensure you order enough materials. Always order slightly more than calculated to account for cutting and mistakes.
Rafter spacing is the distance between the centers of adjacent rafters. Common spacings are 12", 16", or 24" on center. 16" on center is most common for residential construction. The spacing affects how many rafters you need and impacts roof strength.
Plan area is the flat, horizontal area covered by the roof (like the footprint). Surface area is the actual area of the sloped roof surface, which is larger because it accounts for the slope. Surface area is what you need for material calculations.
Hip rafters run diagonally from the corner of the building to the ridge. The calculator uses the formula: hip rafter = common rafter × 1.414 (square root of 2). This accounts for the 45-degree angle of hip rafters in standard hip roofs.
Waste factor accounts for material lost to cutting, mistakes, overlaps, and irregular roof features. A 10% waste factor is standard, but complex roofs with many valleys, hips, or dormers may need 15-20%. It's always better to order slightly more than run short.