Understanding how to work out pitch of roof in degrees is essential for any construction or roofing project. Whether you’re planning a new build, replacing roofing material, or calculating rafter length, converting between pitch ratios and degrees ensures accurate measurements and proper material selection.
Roof pitch is typically expressed as a ratio in the roofing industry—such as 6/12 or 8/12—but many applications require the pitch angle in degrees. This guide explains the formulas, methods, and tools you need to calculate roof pitch accurately and convert it to degrees.
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Skip the manual maths—Chippy Tools converts roof pitch to degrees automatically and calculates rafter lengths in seconds.
What Is Roof Pitch and Why Measure It in Degrees?
Roof pitch describes the steepness or slope of a roof surface. In Australia and North America, the roofing industry typically expresses pitch as a ratio of rise over run—specifically, how many inches (or millimetres) the roof rises vertically for every 12 inches (305 mm) of horizontal distance.
For example, a 6/12 pitch means the roof rises 6 inches (152 mm) for every 12 inches (305 mm) of horizontal run. However, when working with angle cuts, setting saw bevels, or communicating with engineers, you’ll often need the pitch angle in degrees instead.
Converting roof pitch to degrees is particularly useful for cutting rafters at the correct pitch, determining roofing material suitability based on minimum pitch requirements, calculating solar panel installations, and ensuring proper water drains off the roof surface.
The Formula to Calculate Roof Pitch in Degrees
To convert a pitch ratio to degrees, you need to find the roof angle using basic trigonometry. The formula uses the inverse tangent (arctangent) function.
Pitch Angle (degrees) = arctan(rise ÷ run)
For standard pitch x 12 notation, the formula simplifies to arctan(pitch ÷ 12). For a 6/12 pitch, you would calculate arctan(6 ÷ 12) = arctan(0.5) = 26.57 degrees.
Most scientific calculators have an arctan or tan⁻¹ button. Simply divide the rise by the run, then press the inverse tangent function to get your angle in degrees.
Skip the Trigonometry
Chippy Tools handles all roof pitch calculations automatically—just enter your rise and run values to get instant degree conversions.
Roof Pitch to Degrees Conversion Table
This quick reference table shows common pitch x 12 ratios and their equivalent angles in degrees.
| Pitch (Rise/Run) | Roof Angle (Degrees) | Slope Type |
|---|---|---|
| 1/12 | 4.76° | Low slope |
| 2/12 | 9.46° | Low slope |
| 3/12 | 14.04° | Low slope |
| 4/12 | 18.43° | Standard pitch |
| 5/12 | 22.62° | Standard pitch |
| 6/12 | 26.57° | Standard pitch |
| 7/12 | 30.26° | Moderate |
| 8/12 | 33.69° | Moderate |
| 9/12 | 36.87° | Steeper pitch |
| 10/12 | 39.81° | Steeper pitch |
| 12/12 | 45.00° | Steep |
A completely flat roof would theoretically be 0/12 pitch at 0 degrees, though even a flat roof typically has a slight slope of at least 1/4:12 to ensure water drains properly.
How to Measure Roof Pitch From the Ground or Attic
Before you can calculate roof pitch in degrees, you need accurate measurements of the rise and run. There are several methods to measure roof pitch depending on your access.
Measuring From the Attic
If you have attic access, this method provides the most accurate measurements. Place a spirit level horizontally against the underside of a rafter, ensuring it’s perfectly level. Measure 12 inches (305 mm) along the level from where it touches the rafter—this is your run. From the end of that 12 inches, measure the rise vertically up to the rafter surface. If you measure the rise as 6 inches (152 mm), you have a 6/12 pitch.
Measuring From the Roof Surface
Working safely on the roof, place a spirit level on the roof surface and level it horizontally. Measure 12 inches (305 mm) along the level, then measure the vertical rise from the level down to the roof at that point. This method works well but requires appropriate safety equipment and fall protection.
Using a Speed Square
A speed square is a triangular tool commonly used in construction that can measure roof pitch directly. Place the pivot point at the edge of the rafter and read the pitch angle where the rafter intersects the degree scale. Many speed square tools display both pitch ratio and degrees, making conversion unnecessary.
Measure Once, Calculate Everything
Enter your rise and run measurements into Chippy Tools and instantly get pitch ratio, degrees, rafter length, and roof pitch multiplier values.
Calculating Rafter Length Using Roof Pitch
Once you know the pitch of a roof, you can determine the length rafters need to be for your building project. The roof pitch multiplier streamlines this calculation.
Rafter Length = Horizontal Run × Roof Pitch Multiplier
The multiplier accounts for the extra length required as the roof rises at an angle. For a 6/12 pitch, the multiplier is 1.118. If your horizontal distance from the wall to the ridge is 15 feet (4.57 m), your rafter length would be 15 × 1.118 = 16.77 feet (5.11 m) plus any overhang.
Steeper roofs require longer rafters. A 12 pitch roof (45 degrees) has a multiplier of 1.414, meaning rafters are approximately 41% longer than the horizontal run.
Why Roof Pitch Matters for Your Project
Selecting the correct pitch affects multiple aspects of construction and ongoing building performance.
Water Drainage and Weather Protection
Roof slope determines how efficiently water drains from the surface. Steeper pitch angles shed rain faster, while low slope roofs rely on membrane materials to prevent pooling. In snow prone regions, steeper roofs also shed snow more effectively, reducing the structural load from heavy snowfall.
Roofing Material Requirements
Different materials have minimum roof pitch requirements. According to the International Residential Code, asphalt shingles can be installed on pitches as low as 2/12 (9.46 degrees) with double underlayment, though standard installation requires at least a 4/12 pitch (18.43 degrees). Metal roofing panels typically need a minimum 3/12 pitch, while standing seam systems can work on slopes as low as 1/4:12. Tiles and slate often need steeper pitch angles to prevent water infiltration.
Loft Space and Usability
A steeper pitch creates more usable loft space beneath the roof. If you’re planning an attic conversion, you’ll need sufficient roof angle to achieve adequate headroom at the highest point of the space.
Aesthetic and Architectural Style
The pitch of a roof significantly influences a building’s appearance. Low slope designs create a modern aesthetic, while traditional homes often feature steeper roofs ranging from 8/12 to 12/12 pitch.
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Common Roof Pitch Examples in Construction
Different building types typically use different roof pitch ranges. Residential homes commonly use pitches between 4/12 and 9/12 (18–37 degrees), providing a balance of drainage, material options, and loft space.
Commercial buildings often feature low slope or nearly flat roof designs at 1/12 to 3/12 pitch (5–14 degrees). These require specialised membrane roofing to prevent leaks.
Garages, carports, and sheds frequently use 3/12 to 4/12 pitch, while steep architectural designs like A-frame cabins may use 12/12 pitch or greater. Step walls where a roof meets a vertical wall surface require precise pitch calculations to ensure proper flashing installation.
Using a Roof Pitch Calculator
While manual calculations work, a roof pitch calculator eliminates errors and saves time. Enter your rise and run measurements, and the calculator instantly returns the pitch ratio, angle in degrees, roof slope percentage, and roof pitch multiplier for rafter calculations.
Chippy Tools includes a comprehensive roof pitch calculator that handles all conversions automatically. Simply input your measured total rise and horizontal length, and the app calculates everything you need—including rafter length and surface area for material estimates.
Tips for Accurate Roof Pitch Measurement
Getting precise rise run measurements is essential for reliable calculations. Use a spirit level that’s at least 12 inches (305 mm) long to ensure accurate horizontal reference. Take multiple measurements at different points along the roof to confirm consistency—variations may indicate sagging or structural issues.
When using a tape measure, keep it taut and perpendicular for vertical rise measurements. Digital angle finders can also measure the roof angle directly, providing results in degrees without calculation.
For existing roofs where access is limited, you can find roof pitch by measuring the horizontal distance from the wall to the ridge and the vertical distance from ceiling to the highest point of the roof framing in the attic.
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Summary
Learning how to work out pitch of roof in degrees is straightforward once you understand the relationship between rise, run, and angle. Use the formula arctan(rise ÷ run) to convert any pitch ratio to degrees, or refer to a conversion table for common values like 4/12 (18.43°), 6/12 (26.57°), or 12/12 (45°).
Accurate measurements using a spirit level, tape measure, or speed square ensure reliable results. Whether you’re determining rafter length, selecting the right roofing material, or verifying minimum pitch requirements, understanding roof pitch in degrees helps you complete construction projects with confidence.
Frequently Asked Questions
- How many degrees is a 12% slope?
- A 12% slope equals approximately 6.8 degrees. To convert percentage slope to degrees, use the inverse tangent formula: degrees = arctan(12/100) = 6.84°. Note that a 12% slope is different from a 12/12 pitch—percentage slope measures vertical rise per 100 units of horizontal distance.
- Is a 12/12 roof a 45 degree angle?
- Yes, a 12/12 roof pitch is exactly 45 degrees. This occurs because the rise equals the run—the roof rises 12 inches (305 mm) for every 12 inches of horizontal distance, creating a perfect 1:1 ratio. Using the formula arctan(12÷12) = arctan(1) = 45°.
- What degree is a 7 pitch roof?
- A 7/12 pitch roof equals approximately 30.26 degrees. This is calculated using arctan(7÷12) = 30.26°. A 7/12 pitch is a popular choice in residential construction as it provides good water drainage, adequate loft space, and works well with most roofing materials including asphalt shingles.
- How to figure a 4/12 pitch roof?
- To calculate a 4/12 pitch roof in degrees, divide the rise by the run and find the inverse tangent: arctan(4÷12) = 18.43 degrees. A 4/12 pitch means the roof rises 4 inches (102 mm) for every 12 inches (305 mm) of horizontal run. This is the minimum pitch for standard asphalt shingle installation without special underlayment requirements.
- What tools do I need to measure roof pitch?
- To measure roof pitch, you'll need:
- A spirit level (at least 12 inches/305 mm long)
- A tape measure
- A speed square (optional but helpful)
- What is the minimum roof pitch for different materials?
- Minimum pitch requirements vary by roofing material:
- Metal roofing (lapped panels): 3/12 (14°) minimum
- Standing seam metal: 1/4:12 to 1/2:12 (1.2°–2.4°)
- Asphalt shingles: 2/12 (9.5°) absolute minimum with double underlayment; 4/12 (18.4°) for standard installation
- Clay tiles: 4/12 to 5/12 (18.4°–22.6°)
- Flat roof membranes: 1/4:12 (1.2°) minimum for water drainage
- Why does roof pitch matter in construction?
- Roof pitch is an important factor in construction because it determines:
- Water drainage efficiency
- Snow load capacity in snow prone regions
- Roofing material suitability
- Loft space and attic usability
- Rafter length and material costs
- How do I convert roof pitch to a roof pitch multiplier?
- To find the roof pitch multiplier, use the formula: √(1 + (rise/12)²). For example, a 6/12 pitch: √(1 + 0.5²) = √1.25 = 1.118. Multiply your horizontal length by this factor to calculate rafter length. A roof pitch calculator automates this conversion instantly.