How to Measure the Slope of Your Roof

Measuring the slope of a roof—also called the roof pitch—is essential for everything from ordering materials to designing drainage and ensuring proper installation. Whether you're a homeowner, contractor, or DIYer, understanding roof slope is a straightforward process once you know the method.

What Is Roof Slope (Pitch)?

Roof slope describes how steep a roof is. It’s typically expressed as a ratio:

Rise : Run

• Rise = how many inches the roof goes up vertically
• Run = how many inches it goes horizontally (usually 12 inches)
  

Example: A “6/12 pitch” means the roof rises 6 inches for every 12 inches of horizontal distance.

Method 1: Measuring Roof Slope from Inside (Attic Method)

This is the safest and most common method since you don’t need to climb onto the roof.

What You’ll Need:

• Tape measure
• Level (12-inch or longer)
• Pencil or marker
  

Steps:

1. Go into your attic and locate a rafter.
2. Hold your level horizontally against the underside of the rafter. Meeting at the base of the rafter.
3. Measure 12 inches along the level (this is your run).
4. From that 12-inch mark, measure vertically up to the rafter (this is your rise).

Method 2: Measuring Roof Slope from the Roof Surface

If attic access isn’t available, you can measure directly on the roof—but be cautious.

Steps:

1. Place your level flat on the roof surface.
2. Measure 12 inches along the level.
3. From the 12-inch mark, measure straight down to the roof surface.
4. That number is your rise.

Method 3: Using a Framing Square

A framing square can simplify the process.

Steps:

1. Place the square so one leg runs horizontally (12 inches).
2. Let the vertical leg touch the roof surface.
3. Read the rise directly where the roof meets the vertical leg.
   

This method is commonly used by builders and roofers for quick measurements.

Method 4: Using a Digital Pitch Gauge or App

Modern tools make this even easier:

• Digital angle finders
• Smartphone apps (using your camera or gyroscope)
  

These tools give you the slope in degrees, which you can convert to pitch if needed.

Why Roof Slope Matters

Understanding your roof pitch helps with:

• Material selection (metal panels, shingles, etc.)
• Water drainage performance
• Structural design and load handling
• Aesthetic and architectural planning
  

For example, low-slope roofs require different sealing techniques than steep roofs.

Common Roof Pitch Ranges

• Low slope: 2/12 – 4/12
• Conventional: 4/12 – 9/12
• Steep slope: 9/12 and above
  

Pro Tips

• Always measure twice to ensure accuracy
• Use a longer level (24") for better precision
• Record measurements in inches for consistency
• If ordering custom materials (like metal panels or railings), double-check your pitch
  

Final Thoughts

Measuring roof slope is a simple but critical skill. With just a level and a tape measure, you can determine your roof’s pitch in minutes—no advanced tools required.