New Zealand · metal roofing
Roof pitch calculator
Pitch is arctan(rise ÷ run). Useful. Insufficient. Pair it with the profile or you still do not know if the roof can be clad.
Measure a horizontal run (often 1.000 m) and the rise over that run. Degrees = atan(rise/run). Slope length of the common rafter is run / cos(pitch). NZ drawings, CoP tables and manufacturer sheets are in degrees, not in 4/12.
This page still runs the full takeoff because a pitch without a profile is trivia. Change the rise by dragging the pitch control and watch the min-pitch flag on corrugate vs Six Rib. That is the actual decision on a lot of garages.
CoP reminder: the number on the truss is design pitch. Cladding pitch is as-laid, after deflection. Wide bays can take a legal 8° drawing below the corrugate table.
FAQ
What is 15° as a ratio?
About 1 in 3.7, or a 268 mm rise in 1.000 m of run. This site does not convert to imperial 4/12 charts on purpose.
How do I measure pitch on an existing roof?
From the loft: level a 1 m stick along the run, measure plumb rise. From the ground: a pitch app is a hint, not a takeoff input. From drawings: use the stated degrees and then think about deflection.