The pitch of your roof is a measure of how steep it is, and it’s important for more than just appearance. Roof pitch (sometimes more correctly called slope) determines how easily water runs off a roof during a storm and what type of roofing materials the roof can support.
Luckily, it’s pretty simple to calculate your roof pitch yourself. All you need is a tape measure, a spirit level, a pen, a piece of paper, and our calculator. Keep reading, and we’ll teach you how to use these tools to calculate your roof’s pitch. We’ll also explain what your roof’s pitch means for your roof and your future home improvement projects.
Roof Pitch Glossary
To better understand the rest of this guide, you should first get familiar with these terms:
Run
Run is the measurement of the horizontal distance between the leftmost and rightmost points of a right triangle. In roofing, it’s standard to compare 12 inches of run against a roof’s vertical rise.
Rise
Rise is a measurement of the vertical distance between the lowest and highest points of a right triangle. In roofing, the rise is usually defined as how high a roof climbs upward over 12 inches of horizontal run.
Span
Span: A roof’s span is the entire horizontal distance between one edge of the roof and the other. Because it’s also a measurement of horizontal space, span is similar to run, though run is usually just a small portion of a roof’s span.
Slope
Slope is a measurement of how steep a triangle is, and in roofing, it’s usually written out as a rise/run ratio in inches. A triangle with a 12-inch horizontal run and a four-inch vertical rise will have a 4/12 (sometimes written as 4:12) roof slope, meaning it rises four inches for every 12 inches it runs. In the modern roofing industry, the slope is often called “pitch” instead.
Pitch
While pitch historically referred to the relationship between a roof’s entire span and its entire rise (instead of just a section of the roof), it is now used synonymously with “slope” in the roofing industry. In fact, slope is more commonly called pitch by many roofers these days. Because of this, we’ll simply refer to “slope” as “pitch” throughout this article.
How to Calculate Roof Pitch: 2 Methods
You only need a few everyday tools to take measurements and find your roof’s pitch.
What you need
You can’t accurately determine your roof’s pitch by just eyeballing it, and accuracy is key when working on your roof. Luckily, you just need a few tools to get precise measurements:
Method 1: Calculate roof pitch from atop the roof
Measuring your roof’s pitch is as simple as finding its rise and run. Remember, rise is vertical distance, and run is horizontal. For every foot that your roof extends horizontally, it rises "x" amount of inches.
To determine the "x," use this simple measuring technique:
Step 1: Carefully access your roof using your ladder.
Step 2: Measure 1 foot up from the base of the roof using your measuring tape. This will give you the horizontal run.
Step 3: Place one end of your level at the 1-foot mark, but make it create an "L" shape away from your roof by suspending the opposite end in the air.
Step 4: Once the bubble of air in the level’s horizontal vial is in the middle, measure from the bottom of the level to the top of the roof. The distance you measure will be your roof’s vertical rise.
Step 5: Enter your measurements into our calculator to get your results.
For example, if what you measured for the rise is six inches, then the pitch of the roof is 6/12. This means that for every 12 inches of horizontal length of the roof, the roof rises six inches.
Roofs with steeper pitches will have a higher rise number, say 10/12. Roof pitches can also be much lower, and they can be as low as 2/12 for roofs with asphalt shingles or even lower for metal roofs or gambrel-style homes with roofs that have many differently-pitched sections.
If your entire roof is simple and uniformly shaped (it doesn’t feature differently-pitched eaves, overhangs, or dormers), you just have to take pitch measurements once, and you can gather them just about anywhere on your roof.
If, however, your roof has various features that each have its own pitch, you’ll need to take measurements of every roof area and calculate each one separately to get a complete assessment of your roof’s various pitches.
Method 2: Calculate roof pitch from inside the attic
Image source: Reddit
The underside of your roof will have the same pitch as the top, so you can take your pitch measurements along a rafter length in your attic.
If you cannot access your roof or don’t feel comfortable doing so, you can safely measure your roof pitch using a rafter or a roof truss within your attic.
Step 1: Access your attic and find a roof rafter or truss. It will be a wooden beam that runs diagonally along the ceiling of your attic.
Step 2: Measure 12 inches of horizontal run up the beam from your attic floor.
Step 3: To find the vertical rise of your roof, start at the 12-inch mark you measured on your truss and simply measure vertically downward to the attic floor.
Step 4: Put your measurements into our calculator to find your roof’s pitch.
Say the distance from the floor of your attic to the 12-inch mark on your rafter is 6 inches. This would mean your roof pitch is 6/12.
As before, if your roof has multiple structural features with different pitches, you’ll also need to separately find the pitches for each one by repeating this process.
Roof Pitch Chart
Roofs come in all shapes and pitches, though some pitches are more common than others.
The pitch of a roof can have a significant impact on its structural integrity, its ability to support different roofing materials, and its ability to quickly shed water, ice, and other debris. Depending on what type of roof you have, it will have a different pitch.
Flat roofs or low pitch/low slope roofs will typically have a lower ratio and fraction, usually from 1/12-2/12.
The most common pitch for standard gable roofs is between 4/12 and 8/12. This pitch provides enough slope for adequate runoff while also providing the necessary stability for roofing materials like shingles and tiles.
An exceptionally steep roof pitch can reach 18/12 or higher. It sheds snow buildup and drains water more efficiently than a standard roof.
Roof pitch factor
If you know the pitch of your roof, you can use it to calculate its actual surface area. Because pitched roofs are angled, their surface area is larger than their footprint. The roof pitch factor is a multiplier used to account for this extra area. The steeper the pitch, the higher the factor.
Use the table below to find your pitch factor and the valley & hip multiplier for more complex roof shapes:
The Best Roof Pitch for Your Region
If you live in a region with frequent rain or snowfall, then you’ll want a relatively steep pitch to your roof to promote healthy runoff. This will prevent water from pooling on your roof (as long as you keep your gutters in good shape) and ice from weighing on your rafters. Generally, a roof pitch steeper than 6/12 will serve you well in areas where inclement weather is common.
If you live in an arid area, though, you could very well get a lower roof pitch. Most residential roofs don’t feature pitches more gradual than 4/12 because they can have runoff issues. Still, if your region never sees snow and rarely gets any rainfall, you could get away with a flatter roof if you get the right roofing materials.
Materials That Work Best With Different Roof Pitches
Roofing materials for flat roofs
If your home has a flat roof, then your options for roofing materials are fairly limited. Flat roofs don’t drain water very effectively, so shingles and tiles are more likely to leak on flat roofs. Additionally, flat roofs typically can’t support as much weight as roofs with steeper pitches, so heavy roofing materials are usually out of the question.
For these reasons, there are only two roofing materials that work well with flat roofs:
Roofing materials for pitched roofs
If your roof has a steeper pitch, you have a lot more options for what you can cover it with. The table below lists the minimum required pitch for various roofing materials.
Be aware, though, that minimum roof pitch can vary depending on the manufacturer who crafted your roofing materials, and some materials require additional roofing reinforcement. This means you should talk with a roofer about which materials are actually right for your roof.
Minimum roof pitch for different roofing materials
Roofing material | Average minimum roof pitch |
2/12 | |
2½/12 | |
4/12 | |
2½/12 | |
3/12 |
Calculating Your Roof’s Pitch
Now that you know how to find the pitch of your roof, you’re ready to take the next step in your roofing project. If you want to repitch your roof because its current pitch doesn’t meet your needs, that is an option, though roof repitching is a costly and difficult process.
FAQ: Roof Pitch
You can calculate your roof pitch by measuring the vertical rise over a 12-inch horizontal run. For example, if your roof rises 6 inches for every 12 inches of run, the pitch is 6/12. You can measure this using a level, tape measure, and a framing square, or use a pitch calculator app by entering the rise and run. If you have the angle of your roof rather than the rise and run, you can use the arctan (arctangent) function to find the pitch. The pitch, as a ratio, is equal to the tangent of the roof's angle. Therefore, to find the angle from a known rise and run, you would use arctan(rise/run). For instance, if your roof has a rise of 6 and a run of 12, the angle is arctan(6/12) or arctan(0.5), which is approximately 26.57 degrees. Conversely, if you know the angle (e.g., 26.57 degrees), the tangent of that angle (tan(26.57°)) will give you 0.5, which translates to a 6/12 pitch.
The golden rule for roof pitch is to ensure adequate water runoff and structural safety. In most climates, a minimum pitch of 4/12 (a rise of 4 inches per 12 inches of run) is ideal for asphalt shingles, as it sheds water efficiently without compromising walkability or material compatibility.
A 5-degree slope over a 1-meter horizontal run gives a vertical fall of approximately 87 mm. You can calculate it using this formula:Fall = tan(5°) × 1000 mm ≈ 87.5 mm
The correct pitch depends on your roofing material, climate, and architectural style. Low-slope roofs (1/12 to 3/12) are common on modern and commercial buildings. Standard residential roofs typically range from 4/12 to 8/12, which balance water runoff and aesthetic appeal. Steep roofs (above 9/12) are often used in snowy or rainy climates for better drainage.
Irena is an industry analyst and financial content specialist at Fixr.com, where she transforms complex data into clear insights to help homeowners make smarter financial decisions. With a background in personal finance research and writing since 2018, she brings years of experience in helping readers understand how to maximize their home investments. Her work has been featured on reputable websites, including Washington Examiner, Yahoo Finance, Fox40, and Forbes.