Have you ever wondered why some houses have steep roofs while others are rather flat? The angle of your roof, known as roof pitch, affects more than you think—from aesthetics to structural integrity. It can even impact your wallet regarding material and labor costs, energy efficiency, and resale value.

Our guide explains how to calculate roof pitch when installing a new roof or replacing an existing one. We also explore the most common roof pitches and which materials work best with different designs to help you plan your project.

---

What Is a Roof Pitch?

Roof pitch is your roof’s incline, expressed as a fraction. Roofing contractors base this calculation on how many inches your roof rises vertically for every 12 inches it runs from end to end (horizontally). For example, a 6/12 pitch means that for every 6 inches a roof rises vertically, it extends 12 inches horizontally. 

Although many use the terms interchangeably, a roof’s pitch differs from its slope. You calculate the pitch based on the roof’s vertical rise and horizontal span, while the slope considers the rise and run, which is only a portion of the span. A single roof can have multiple slopes but only one pitch.

---

Why Does Roof Pitch Matter?

Roof pitch isn’t just an aesthetic choice—it directly impacts several aspects of your roofing system. Here are some of the practical roof pitch implications:

• Weather resistance: Steeper pitches excel at shedding rain and snow, minimizing the risk of leaks and water damage. Low-slope roofs are more vulnerable to ponding in areas with heavy precipitation (rain or snow).
• Material compatibility: Different roofing materials have specific pitch requirements. Most asphalt shingles, for example, need at least a 4/12 pitch for proper drainage, while metal panels might only need a 3/12 pitch.
• Structural integrity: Regions with heavy snow loads require a correctly pitched roof to withstand the weight and prevent potential collapse. The wrong pitch could compromise the roof’s strength.
• Durability and lifespan: A roof with the right pitch for your climate will generally last longer and require less frequent roof repair. Water ponding or excessive snow buildup can drastically shorten a roof’s life span.
• Energy efficiency: Roof pitch can influence attic ventilation, which impacts your home’s overall energy efficiency. In warmer climates, a steeper pitch encourages better airflow beneath the roof and reduces the strain on your air conditioning system. 
• Gutter sizing: Steeper roofs shed water more quickly, directing more water into the gutters during rainfall. Larger gutters and downspouts may be necessary to prevent overflow and potential damage to your home.

Choosing a roof pitch is about finding the perfect balance between your area’s climate, the desired architectural style, and budget.

---

How Do You Determine Your Roof Pitch?

You can calculate roof pitch by dividing the roof’s rise by its span. The vertical rise is the measurement from the roof’s lowest point to the highest point, and the span is the horizontal distance between the roof’s exterior walls.

Tools and Safety Considerations

You’ll need to use a ladder and observe safety precautions when measuring your roof for shingles or pitch. Alternatively, you can measure from inside your home if you can access your roof’s rafters. Here’s what you need to measure from the outside:

• Tape measure or ruler
• 12-inch level
• Pen and paper
• Ladder (if measuring from the roof)
• Flashlight (if measuring from the attic)
• Bag or bucket to carry small items (optional)

Remember, never work on a roof alone. Have someone nearby to assist and hold the ladder for stability. Avoid measuring your roof in wet or icy conditions. Hire a roofing professional if you’re uncomfortable walking on the roof or accessing the attic.

Step-by-Step Instructions

Once you have checked the weather and collected the necessary items, follow these instructions to calculate the roof pitch:

1. Access the roof. Securely place your ladder against the house and carefully climb to reach the roof. Ensure the ladder is stable and extends beyond the roofline for safe dismounting.
2. Position the level. Hold a 12-inch level perfectly horizontal, with the left end touching the surface of your roof to create a gap between the other end of the level and the roof’s surface.
3. Measure the rise. Measure the vertical distance from the roof surface to the 12-inch mark on the level. This measurement is the roof’s rise.
4. Calculate the pitch. Divide the rise by 12 to get the pitch expressed as a fraction. For instance, a 6-inch rise would mean a 6/12 pitch.

Measuring from inside is a safer option if you have access to your attic. Here’s how to do it:

1. Find the rafters. Locate your attic access point. Enter the attic and locate the exposed roof rafters (the sloped wooden beams supporting the roof).
2. Position the level. Place one end of a 12-inch level against the rafter’s bottom edge, ensuring it’s perfectly level. If you can’t access a rafter, hold the level so that one end touches the sheathing or decking (the structural boards beneath your shingles).
3. Measure the rise. Measure the vertical distance from the other end of the level up to the rafter or the roof deck. This gap represents the rise.
4. Calculate the pitch. Divide the rise by 12 to calculate the roof pitch. Alternatively, you can measure the total rise from the ceiling joist to the roof’s peak and divide it by the horizontal run of a single rafter.

---

Most Common Roof Pitches

Roof pitches fall into three categories: low, conventional, or steep. Most residential roofs have a pitch between 2/12 and 12/12. Low-slope or flat roofs have a pitch of 3/12 or lower. Conventional roofs have a pitch between 4/12 and 9/12, while steep roofs have a pitch of 10/12 or higher.

The most common roof pitches for residential homes are between 4/12 and 8/12. We’ll review some of those pitches below:

Your roof’s pitch influences its overall design, which is central to a home’s appearance. Here are a few common roof shapes and their typical pitches:

• Flat roofs: Despite the name, flat roofs have a subtle slope (3/12 or lower) for water drainage. Both residential and commercial buildings can have flat roofs.
• Mono-pitch roofs: Mono-pitch roofs feature a single sloping plane. They are often seen with a 1/12 pitch in modern architecture, but steeper slopes are possible.
• Hip roofs: Hip roofs have slopes on all four sides of the house, typically with a moderate pitch around 4/12. The four slopes meet at a ridge in the middle of the roof.
• Gable roofs: Gable roofs feature two main sloping sections that form a peak. They often have a pitch of 3/12 or steeper.
• Mansard roofs: Mansard roofs have two distinct slopes on each side of the building. The lower slope is steeper—sometimes nearly vertical—while the upper slope has a much lower pitch.

---

Of course, roof pitch is not the only factor to consider when selecting roofing materials. For a brief overview of the four most popular roofing materials and how they compare on other key metrics, check out the video below with general contractor Tom Silva:

---

What Roof Pitch Is Best for You?

Choosing the right roof pitch greatly affects your roof’s performance, durability, and aesthetics. Although roof style matters, you must consider a few other factors before deciding which roof pitch is best. For instance, steeper roofs generally require more materials and a more complex design, increasing costs.
You should also consider your location and its climate. A roofing contractor will likely recommend a conventional or steep roof pitch for efficient drainage if you live somewhere with heavy snowfall or rain. A steeper pitch prevents water ponding from the extra weight of accumulated snow, safeguarding your roof’s structure.

---

Our Conclusion

Understanding pitch lets you make informed decisions regarding roof replacement, repairs, or potential modifications. The ideal pitch for your home depends on various factors, including your local climate, architectural style preferences, and budget. Steeper pitches excel in areas with heavy snowfall or rain, while low-pitch roofs offer cost advantages and a modern aesthetic. A conventional roof pitch, such as a 6/12 pitch, is easy to install, fares well in most climates, and is aesthetically pleasing. 

Always consult a professional roofer before changing your roof pitch. They can assess your existing roof, recommend an optimal pitch based on your needs, and ensure it is constructed or replaced following proper building codes and best practices.

---

FAQ About Common Roof Pitches

To share feedback or ask a question about this article, send a note to our Reviews team at reviews@thisoldhousereviews.com.