Advanced Roof Pitch Estimator

Unit System

Input Mode

Building Span (width, optional)

Building Length (optional)

Overhang Each Side (optional)

Rafter Spacing Along Length (optional)

Primary Inputs (depending on selected mode)

Rise

Run

Pitch (X in 12)

Angle (degrees)

Slope (%)

Example Roof Pitch Calculations

Use these sample values to verify and understand the estimator outputs.

Example	Rise	Run	Pitch (X in 12)	Slope (%)	Angle (°)
Low slope roof	2	12	2 in 12	16.67%	9.46°
Standard residential	6	12	6 in 12	50.00%	26.57°
Steep roof	9	12	9 in 12	75.00%	36.87°

What Is Roof Pitch? Rise, Run, and Slope Explained

Roof pitch describes how steep a roof is by comparing vertical rise to horizontal run. For example, a 6 in 12 pitch means the roof rises 6 units for every 12 units of run.

From this ratio, the calculator derives slope percentage and angle in degrees. Understanding all three views helps match manufacturer requirements and local code limits.

How to Measure Roof Pitch Step by Step (Inside or Outside)

Method 1: Measuring from the Roof Surface (Outside)

Place a spirit level horizontally on the roof surface.
Mark 12 inches (or 300 mm) along the level from the contact point.
At that mark, measure vertically from the level down to the roof surface.
The vertical reading is the rise; express as rise in 12 units.

Method 2: Measuring from the Attic (Inside)

Hold a level horizontally against a rafter and mark 12 inches along it.
From that mark, measure straight up to the underside of the rafter.
This vertical distance is the rise over 12; enter it into the estimator.

Always measure on a safe, stable surface. Use fall protection when working outside.

Roof Pitch Formula: Convert Pitch to Degrees and Percent

Given pitch as X in 12:

Slope (%) = (X / 12) × 100
Angle (degrees) = arctan(X / 12)

To invert:

Pitch (X in 12) from slope (%) = (Slope / 100) × 12
Pitch (X in 12) from angle = tan(Angle) × 12

The estimator applies these conversions instantly whenever you change input modes.

Roof Pitch Chart: Degrees, Percent Grade, and x/12 Table

Use this quick reference table for common residential and commercial roof pitches. Values are approximate but sufficient for planning, quoting, and communicating with suppliers.

Pitch (x/12)	Angle (°)	Slope (%)
1 / 12	4.76°	8.33%
2 / 12	9.46°	16.67%
3 / 12	14.04°	25.00%
4 / 12	18.43°	33.33%
5 / 12	22.62°	41.67%
6 / 12	26.57°	50.00%
7 / 12	30.26°	58.33%
8 / 12	33.69°	66.67%
9 / 12	36.87°	75.00%
10 / 12	39.81°	83.33%
12 / 12	45.00°	100.00%

Understanding Low, Medium, and Steep Roof Pitches

Low-slope: 1/12 to 3/12 (about 4.8°–14°). Requires special membranes and careful drainage; not ideal for most shingles without extra detailing.
Medium-slope: 4/12 to 8/12 (about 18°–34°). Common for residential roofs; good water shedding and easy material availability.
Steep-slope: 9/12 and above (about 37°+). Great for snow shedding and attics, but increases material waste and labor difficulty.

Use this estimator to test alternatives and confirm pitches align with local climate, aesthetics, and manufacturer guidelines.

Formula Used

These are the core relationships used by the roof pitch estimator for a simple gable-style roof:

Pitch (X in 12) = (Rise / Run) × 12
Slope (%) = (Rise / Run) × 100
Angle (degrees) = arctan(Rise / Run)
Common rafter length = √(Run² + Rise²)
Rafter with overhang = √((Run + Overhang)² + Rise²)
Two-slope roof area = 2 × CommonRafterLength × BuildingLength

Calculations assume straight rafters, uniform pitch, and a simple symmetrical layout. For complex roofs with valleys, hips, or multiple pitches, use this tool per section.

How to Use This Roof Pitch Estimator

Select your preferred unit system: Imperial (feet) or Metric (meters).
Choose an input mode:
- Rise & Run – when you know vertical rise and horizontal run.
- Pitch (X in 12) – common for shingle and framing charts.
- Angle (degrees) – when measured with an inclinometer or app.
- Slope (%) – often found on architectural drawings.
Optionally enter building span and length:
- Span helps determine run automatically for symmetric roofs.
- Length enables automatic roof surface area and rafter count estimation.
Add overhang and rafter spacing if you want rafter length with overhang and approximate rafter counts.
Click Calculate Roof Pitch to generate detailed results.
Use the CSV button to export results for spreadsheets and reports.
Use the PDF button to download a formatted summary for clients or documentation.

Always verify outputs against local building codes, manufacturer requirements, and structural engineering guidelines before construction.