Roof pitch is the angle or steepness of your roof, expressed as a ratio of rise to run
Roof pitch tells you how many inches your roof rises vertically for every 12 inches it travels horizontally. A pitch of 4:12 means the roof rises 4 inches for every 12 inches of horizontal distance. This measurement matters because it affects how water drains, what materials you can use, how much attic space you have, and what safety equipment you need when working on the roof.
You can find your roof pitch by measuring it directly on the roof, checking your building plans, or calculating it from measurements taken inside your attic. The method you choose depends on whether you can safely access your roof and whether you have existing documentation.
Key Takeaways
- Roof pitch is written as a ratio like 4:12, meaning 4 inches of rise for every 12 inches of run.
- You can measure pitch using a level and tape measure on the roof itself, or use a smartphone level app if you have safe access.
- If you cannot safely access the roof, you can calculate pitch from inside the attic by measuring the vertical rise and horizontal span of the rafters.
- Steeper pitches (8:12 and above) shed water faster but require more safety precautions and specialized materials; flatter pitches (under 4:12) are easier to work on but need better drainage systems.
Measuring pitch directly on the roof with a level and tape measure
This is the most straightforward method if you can safely access your roof. You will need a carpenter's level (at least 2 feet long), a tape measure, and a pencil. Start at the lowest point of the roof section you are measuring, or at a spot where you can safely work.
Place the level horizontally on the roof surface. Measure 12 inches along the roof from one end of the level, moving away from the peak. At that 12-inch mark, measure straight up (perpendicular to the roof) until you reach the level. The distance you measure is your rise. For example, if you measure 6 inches up, your pitch is 6:12.
Write down the measurement when ready. If you are measuring multiple roof sections (a house often has different pitches on different sides), measure each section separately and label them clearly. Take measurements in at least two or three spots on the same roof plane to confirm the pitch is consistent.
Using a smartphone level app to find pitch
Many smartphones have built-in level apps or you can read one free from your phone's app store. These apps measure the angle of a surface in degrees, which you can then convert to pitch ratio.
Open the level app and place your phone flat against the roof surface, aligned with the direction the roof slopes (not perpendicular to it). The app will show you an angle in degrees. To convert degrees to pitch, use this formula: pitch = 12 × tan(angle in degrees). For a 30-degree angle, the calculation is 12 × tan(30°) = 6.9, so approximately 7:12 pitch.
This method is faster than measuring with a level, but it is less precise for very shallow pitches. It works best on roofs with pitches between 4:12 and 12:12. Always take multiple readings from different spots to confirm your result.
Calculating pitch from measurements inside the attic
If you cannot safely access the roof exterior, you can measure from inside the attic. You will need a tape measure, a level, and a pencil. This method works best if your attic has exposed rafters you can see and measure.
Find a rafter that runs from the peak of the roof down to the wall. Measure the vertical distance from the peak down to the point where the rafter meets the top of the wall — this is your rise. Then measure the horizontal distance from that same wall to the point directly below the peak — this is your run. Divide the rise by the run, then multiply by 12 to get your pitch ratio. For example, if rise is 6 feet and run is 12 feet, your pitch is (6 ÷ 12) × 12 = 6:12.
Make sure you are measuring along the actual rafter line, not just guessing at angles. Use the level to confirm your vertical measurement is truly vertical. If your attic has collar ties or other bracing, measure from a clear section of rafter.
Reading pitch from building plans and permits
Your original building plans or roof permit often list the roof pitch. Check your homeowner documents, the file you received at closing, or contact your local building department. Many departments keep copies of permits and plans on file and can provide them for a small fee or free.
Call your city or county building permit office and give them your address and the year the roof was built or last replaced. They can tell you whether plans are on file and how to obtain them. This is the most reliable method if documentation exists, because it reflects what was actually built.
If you have had roof work done recently, the contractor's invoice or warranty paperwork may also list the pitch. Roofing companies often document this information for insurance and warranty purposes.
Understanding pitch notation and common roof angles
Pitch is always written as rise:run, with 12 as the standard run. A 4:12 pitch is considered low or shallow. A 6:12 or 8:12 pitch is moderate. Anything 12:12 or steeper is considered steep. Some very steep roofs reach 16:12 or even 20:12.
Shallow pitches (under 4:12) are common on modern homes and are easier to work on, but they require excellent drainage and are prone to ice damming in cold climates. Moderate pitches (6:12 to 8:12) are the most common residential pitch and balance safety, drainage, and material options. Steep pitches (over 12:12) shed water and snow quickly but require special safety equipment and are harder to inspect or repair.
Pitch also determines what roofing materials you can use. Asphalt shingles typically require a minimum pitch of 3:12 or 4:12. Metal roofing can go lower. Flat roofs (technically 0:12 to 1:12) require membrane systems designed to handle standing water.
Safety considerations when measuring roof pitch
Never measure roof pitch on a wet, icy, or steep roof. Wear non-slip shoes with good grip, and use a safety harness or rope if your roof pitch is 8:12 or steeper. If you are not comfortable on a roof, do not attempt to measure — hire a roofer or inspector to do it for you.
Measure during daylight hours when you can see clearly. Avoid measuring near the edges of the roof or near gutters. If you are using a ladder to access the roof, make sure it is stable and secured, and have someone hold it from below.
If your roof is very steep, very high, or in poor condition, measuring from the attic is safer and often more practical. The information you get is just as accurate.
Frequently Asked Questions
What is the difference between pitch and slope?
Pitch and slope mean the same thing in roofing — they both describe the steepness of the roof. Pitch is the term used in residential construction and is expressed as a ratio (4:12). Slope is sometimes used in commercial roofing and is expressed as a percentage or decimal. For practical purposes, you can use the terms interchangeably.
Can I measure pitch from the ground using a photo?
You cannot get an accurate pitch measurement from a ground-level photo because the angle of the photo distorts the roof's actual angle. You need to measure from the roof itself or from inside the attic. Photos can help you estimate whether a roof is shallow or steep, but not the exact pitch.
Why does roof pitch matter for repairs or replacement?
Pitch determines what materials can be used, how long installation takes, what safety equipment is needed, and how much the work costs. Steeper roofs require more labor and specialized equipment, so they cost more to repair or replace. Knowing your pitch helps you get accurate quotes and understand why prices vary between contractors.
Do I need to measure every section of my roof?
If your roof appears uniform from the ground, one or two measurements should be enough. However, many houses have different pitches on different sides or sections. Measure each visibly different section separately to get accurate information for the whole roof.
What if my measurements do not match the building plans?
Roofs sometimes settle or shift over time, or repairs may have altered the original pitch slightly. If your measurements differ from the plans, trust your direct measurement — that is what is actually there now. This matters most if you are planning repairs or replacement.