Pitch, ratio and rafter length from a rise and a run
Type the rise and the run, or the angle, and get the pitch in degrees, the ratio and the rafter length to the ridge.
Reading a roof pitch
A pitch is written three ways: as an angle, as a ratio of rise to run, and as a percentage. Builders in different countries favour different ones, and a drawing often shows only one. The calculator gives all three from any of them.
The rafter length is the hypotenuse of the rise and the run, measured along the slope from the wall plate to the ridge line. Overhangs, the ridge beam and the birdsmouth cut add to or take from it on site.
Minimum pitches come from the roofing material: tiles and slates need more slope than standing seam metal or membranes. Check the manufacturer before the pitch is fixed.
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The numbers are done. Now the image.
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