Choose the value that should update automatically.
Edit pitch, run, rise, and overhang directly on the rafter. Lock the dimensions you want to keep and StructaCAD updates the remaining geometry automatically.
6/12 roof pitch converted to angle, percentage slope and rise/run ratio.
Reference
Degrees and percentage slopes are calculated from each X/12 pitch using the same formulas as the calculator.
| Pitch | Degrees | Percentage slope | Rise/run ratio |
|---|
Measure the vertical rise over a known horizontal run. Divide rise by run to get the slope ratio. To express the same roof as X/12, multiply that ratio by 12.
Example: a 6 in rise over a 12 in run gives 6/12. A 150 mm rise over a 300 mm run gives the same pitch because the ratio is identical.
The roof angle is measured from horizontal. For an X/12 roof pitch, divide X by 12 and apply the inverse tangent.
A 6/12 pitch is approximately 26.57°. The calculator uses the trigonometric conversion directly rather than a hardcoded lookup.
If you know the roof angle, take the tangent of the angle to obtain rise/run, then multiply by 12.
This is useful when an angle is measured from a drawing, inclinometer or digital level.
Roof slope percentage expresses vertical change as a percentage of horizontal run. A 50% slope means the roof rises 0.5 unit for every 1 unit of horizontal run.
Pitch, angle, gradient and percentage slope describe the same geometry in different formats.
The table above lists 1/12 through 12/12 and calculates the corresponding angle and percentage slope. Lower pitches are flatter; 12/12 corresponds to a 45° roof because rise equals run.
Pitch alone does not determine structural adequacy, roofing compatibility or drainage requirements; those depend on the roof system and applicable requirements.
Pitch is commonly written as rise per 12 units of run, such as 6/12. Roof angle expresses the same slope in degrees from horizontal.
Divide the percentage by 100 to get rise/run, then multiply by 12. For example, 50% becomes 0.5 × 12 = 6, or 6/12.
Take the tangent of the angle and multiply by 100. For example, tan(26.565°) × 100 is approximately 50%.
Yes. Rise/run is a ratio, so any matching units work. A rise of 150 mm over a run of 300 mm is the same 6/12 pitch as 6 inches over 12 inches.
Not by itself. Rafter length also requires a horizontal run. Use the Roof Rafter Calculator when you need rafter length, overhang, birdsmouth and layout geometry.