A 6/12 roof pitch has an angle of approximately 26.6 degrees. The notation means the roof rises 6 inches for every 12 inches of horizontal distance, so its slope is 50%. Knowing the angle can help with roof planning, material estimates, and understanding building plans—but roof pitch, angle, and rafter length are related measurements, not interchangeable terms.
What Angle Is a 6/12 Roof Pitch?
A 6/12 roof pitch forms an angle of about 26.6° from horizontal. In common roof-pitch notation, the first number is the vertical rise and the second is the horizontal run, both measured in the same units. A 6/12 roof therefore rises 6 inches over a 12-inch horizontal run.
The angle comes from a right-triangle calculation. The roof surface is the sloping side, the 6-inch rise is the opposite side, and the 12-inch run is the adjacent side. Using the inverse tangent function:
Roof angle = arctan(rise ÷ run) = arctan(6 ÷ 12) ≈ 26.6°
This is the angle between the roof surface and a level horizontal line. It is not the angle between the roof and a vertical wall; that angle is approximately 63.4°.
What 6/12 Roof Pitch Means
Roof pitch describes how steep a roof is. In the United States, it is commonly written as rise over run, such as 6/12 or 6:12. The run is conventionally 12 inches, while the rise can vary. A 6/12 pitch is also described as a “6-in-12” roof.
The ratio can be scaled to other distances. A roof with this pitch rises 3 inches over a 6-inch horizontal run, or 3 feet over a 6-foot run. The essential relationship is a rise-to-run ratio of 1:2.
- Pitch: 6 inches of rise per 12 inches of horizontal run
- Angle: approximately 26.6° from horizontal
- Slope percentage: 50%
- Roof-surface length per 12 inches of run: approximately 13.42 inches
In some contexts, “pitch” has a stricter geometric meaning: rise divided by the roof’s total span. However, residential roof plans and construction conversations in the U.S. typically use pitch notation to mean rise per 12 inches of horizontal run. Checking the drawing’s dimensions or terminology can prevent confusion.
How to Calculate Roof Pitch in Degrees
To convert a roof pitch to an angle, divide the rise by the run and find the inverse tangent. A calculator may label this function “tan⁻¹” or “arctan.” The calculator should be set to degrees, not radians.
- Identify the vertical rise and horizontal run.
- Divide the rise by the run using the same units.
- Calculate the inverse tangent of that ratio.
For a 6/12 roof, the calculation is arctan(6 ÷ 12). The ratio is 0.5, and its inverse tangent is about 26.565°. Rounded to one decimal place, the roof angle is 26.6 degrees.
The same method works for other pitches. For example, a 4/12 roof is arctan(4 ÷ 12), or about 18.4°. An 8/12 roof is arctan(8 ÷ 12), or about 33.7°. The rise-to-run number itself is not the angle: a 6/12 pitch is not a 6-degree roof.
6/12 Roof Pitch Compared With Other Pitches
Comparing common roof pitches makes the 6/12 angle easier to picture. The figures below are approximate; small differences can result from rounding.
| Roof Pitch | Angle From Horizontal | Slope Percentage |
|---|---|---|
| 2/12 | 9.5° | 16.7% |
| 3/12 | 14.0° | 25% |
| 4/12 | 18.4° | 33.3% |
| 6/12 | 26.6° | 50% |
| 8/12 | 33.7° | 66.7% |
| 10/12 | 39.8° | 83.3% |
| 12/12 | 45.0° | 100% |
A 12/12 pitch is a 45-degree angle because its rise and run are equal. A 6/12 roof is less steep: its rise is half its run, so its angle is about 26.6 degrees.
How to Find the Rise and Roof Height
Once the horizontal run is known, the rise of a 6/12 roof is half that distance. If a roof section has a 10-foot horizontal run, its rise is 5 feet. If the run is 14 feet, its rise is 7 feet.
For a symmetrical gable roof, the run is generally measured from the outside wall or bearing point to the ridge along a horizontal line. It is often half the building’s width, but the exact framing dimensions, overhangs, and support locations matter. For example, a building that is 24 feet wide may have a 12-foot run on each side if the ridge is centered and the relevant bearing points are at the exterior walls. At a 6/12 pitch, that run corresponds to a 6-foot rise.
That rise describes the vertical difference between the chosen bearing point and the ridge, not necessarily the building’s total height. Ceiling framing, wall height, ridge details, and other design elements affect the final elevation. Construction plans should govern when precise dimensions are needed.
How to Estimate Rafter Length for a 6/12 Roof
Rafter length can be estimated from the right triangle formed by the horizontal run, the rise, and the sloping roof surface. For a 6/12 pitch, the length of the sloping line is the square root of 12² + 6², or about 13.42 inches for every 12 inches of horizontal run.
This gives a rafter-length factor of approximately 1.118. Multiply the horizontal run by 1.118 to estimate the slope length, before accounting for overhangs, cuts, and connection details.
For example, a 12-foot horizontal run has an estimated roof-surface length of 12 × 1.118, or about 13.42 feet. The calculation measures from the selected starting point to the ridge along the roof slope. A finished rafter may be longer if it includes a tail for an eave overhang.
This is a geometric estimate, not a complete framing specification. Actual member dimensions, bearing points, ridge details, lumber sizes, loads, and local requirements can affect the framing design. For construction, use approved plans or consult a qualified building professional.
How to Measure a Roof’s Pitch
A roof’s pitch can be measured from accessible framing in an attic or, with suitable equipment and training, from the roof surface. A level and tape measure are commonly used for an attic measurement.
- Place a level horizontally against the underside of a rafter.
- Mark a point 12 inches along the level from the rafter.
- Measure vertically from the level at that point to the rafter.
- A 6-inch vertical measurement indicates a 6/12 pitch.
A digital angle finder can measure the roof angle directly. If it reads about 26.6° from horizontal, the pitch is close to 6/12. Measurements may vary slightly because of tool placement, uneven framing, roof sag, or surface irregularities.
Roof work can be dangerous. A 6/12 roof is sloped, and its surface may become slippery from moisture, dust, or debris. Measuring from the ground with a tool designed for that purpose or from accessible framing is safer than climbing onto the roof. Anyone who is not trained and properly equipped should leave roof access to a professional.
Roof Pitch, Slope Percentage, and Degrees Are Different
These terms describe the same roof geometry in different ways, but they are not numerically interchangeable. Pitch is typically expressed as rise per 12 inches of run. Slope percentage is the rise divided by the run, multiplied by 100. The angle is found with the inverse tangent of the rise-to-run ratio.
For a 6/12 roof, the rise-to-run ratio is 6 ÷ 12, or 0.5. Multiplying by 100 gives a 50% slope. Taking the inverse tangent gives approximately 26.6°. A 50% slope does not mean the roof angle is 50 degrees.
Confusing these measurements can lead to mistakes when interpreting plans, using online calculators, ordering materials, or communicating with a contractor. A clear description includes the measurement and its units—for example, “6 inches of rise per 12 inches of horizontal run.”
What a 6/12 Pitch Means for Roofing
A 6/12 pitch is a moderately sloped roof by common residential standards, though descriptions such as “low,” “moderate,” or “steep” are not universal technical classifications. The pitch affects water drainage, roof appearance, access, and the installation requirements of roofing products.
Roofing material requirements vary. Shingles, metal panels, underlayment, and other products can have different minimum-slope rules and installation details. Local building codes and the manufacturer’s current instructions determine what is permitted for a specific roof. A pitch alone does not establish that a particular material is suitable.
For code-related questions, the International Code Council’s model codes provide a starting point, but local jurisdictions adopt and amend codes differently. Product installation instructions and local building officials are important sources for project-specific requirements.
Common Questions About a 6/12 Roof
Is a 6/12 roof the same as a 26.6-degree roof?
They are approximately equivalent when the angle is measured from horizontal. A 6/12 pitch corresponds to about 26.6°. The pitch describes a rise-to-run ratio; degrees describe the resulting angle.
Is a 6/12 roof considered steep?
It is generally described as a moderate residential pitch, but there is no single universal boundary between moderate and steep. Classification varies by trade, product instructions, and context. Regardless of label, roof access requires appropriate safety precautions.
What is the slope percentage of a 6/12 roof?
Its slope is 50% because the rise is 6 divided by the 12-inch run, then multiplied by 100. This percentage is not the angle in degrees.
How many inches does a 6/12 roof rise per foot?
It rises 6 inches for each 12 inches, or one foot, of horizontal run. Over a 10-foot run, the rise is 5 feet.
How long is a rafter on a 6/12 roof?
For each foot of horizontal run, the sloping length is about 1.118 feet. Multiply the actual run by 1.118 for a basic estimate, then account for overhangs and framing details separately.
Reliable References for Roof-Pitch Calculations
The angle and rafter-length figures in this article follow standard right-triangle trigonometry. For project-specific code and material questions, consult local building authorities and the current installation instructions for the roofing product. The International Code Council publishes model building codes, while local jurisdictions determine which editions and amendments apply.