Learn four ways to determine roof pitch using rise and run, an accessible attic rafter, an angle reading or direct roof measurements. Start with the safest method that fits your situation.
The basic method: measure how many inches the roof rises vertically over a 12-inch horizontal run. If the roof rises 6 inches over 12 inches of run, the roof pitch is 6/12, which equals approximately 26.57°.
The best method depends on what parts of the building you can safely reach and how accurate the measurement needs to be.
If the underside of a common rafter is safely accessible, you can measure pitch without walking on the roof surface.
Example: a 6-inch rise over 12 inches of horizontal run gives a 6/12 roof pitch.
On some buildings, the sloped rake at the gable end can be measured from a safely accessible position.
Do not use a ladder or elevated position unless it can be used safely and in accordance with its instructions.
If you already have a reliable roof angle reading from a digital level or inclinometer, you can convert degrees directly into roof pitch.
A reading of about 26.57° converts to approximately 6/12.
Building drawings, framing measurements or existing construction dimensions may already provide enough information to calculate pitch.
Example: 4 ft of rise over 8 ft of run equals 6/12 pitch.
Suppose you place a level horizontally beneath an accessible attic rafter and mark exactly 12 inches of run.
At the 12-inch mark, the vertical distance from the level to the rafter measures 6 inches.
That means the roof rises 6 inches for every 12 inches of horizontal run.
A 6/12 pitch corresponds to an angle of approximately 26.57° and a slope of 50%.
Enter your measured rise and run below to convert the measurement into roof pitch, angle, slope percentage, rafter length and pitch factor.
Enter your roof measurements and calculate instantly.
Accuracy matters, but the safest reliable method should normally be preferred over climbing onto the roof.
Useful when common rafters are exposed and you can safely reach them from inside the building. It avoids walking on the roof surface.
A reliable digital angle measurement can be converted into pitch without manually measuring both rise and run.
Existing building drawings or verified framing dimensions may already provide the rise and run required for calculation.
Small measurement errors can change the calculated pitch, especially when the horizontal reference is short or not level.
Run is horizontal distance. The sloped rafter length is not the same measurement.
Even a small tilt can change the vertical rise reading.
Raised shingles, tiles or uneven surfaces can introduce error.
On a symmetrical gable roof, run is generally one-half of the total building span.
Keep more precision during calculation and round the final pitch or angle afterward.
Additions, dormers and intersecting roofs can have different pitches on different sections.
Use this table as a quick check after taking a measurement.
| Pitch | Rise per 12 in | Angle | Slope |
|---|---|---|---|
| 2/12 | 2 in | 9.46° | 16.67% |
| 4/12 | 4 in | 18.43° | 33.33% |
| 6/12 | 6 in | 26.57° | 50% |
| 8/12 | 8 in | 33.69° | 66.67% |
| 10/12 | 10 in | 39.81° | 83.33% |
| 12/12 | 12 in | 45° | 100% |
The calculators on RoofingPitchCalculator.com use standard right-triangle relationships between horizontal run, vertical rise and the sloped roof line.
For pitch calculations, rise and run are converted into a ratio. Angle is calculated from that ratio, while slope percentage is the rise-to-run ratio multiplied by 100.
Worked examples such as 4/12, 6/12, 8/12 and 12/12 are checked across pitch, angle, slope and pitch-factor outputs so the values remain internally consistent.
Calculator results are measurement references. Actual roofing and framing work may require field verification, structural drawings, manufacturer instructions and applicable building requirements.
Once you know the pitch, these tools can help with the next measurement or conversion.
Quick answers to common roof pitch measurement questions.
If exposed rafters are safely accessible from an attic, measuring a 12-inch horizontal run beneath a rafter and measuring its vertical rise is often a practical method.
Usually not. Attic measurements, existing plans, accessible gable measurements or professional measurement can often determine pitch without walking on the roof.
It means the roof rises 6 units vertically for every 12 units of horizontal run.
Yes. An angle can be converted to pitch using the tangent of the angle. For example, about 26.57° equals 6/12.
No. On a simple symmetrical gable roof, the horizontal run from wall to ridge is generally half of the full span.
Yes. Repeating the measurement helps catch errors caused by an uneven reference surface or a level that was slightly tilted.
Enter rise and run to calculate pitch ratio, roof angle, slope percentage, rafter length and pitch factor.
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