All online tools use javascript to calculate the dimensions. Use at your own risk. If the answers look wrong then verify the answers with a calculator.

This octagon bay window rafter script - calculator will return the octagon baywindow geometry angles and trigonometry rafter measurements for all types of equal and unequal sided octagon baywindow roof framing. The script is limited to 45° baywindow calculations. The plate line must meet at 45° at all intersecting corners.

  The Octagon Rafter Calculator can handle the normal equal sided octagon roofs, where the face wall and side 45 walls are cut and stacked the same. Or it can handle an unequal sided octagon roof where the face wall pitch is different from the 45 side wall pitch, becuse of the different wall plate lengths. When the wall plate lengths are not equal in length, the overhang run for the 45 wall will be different from the face wall overhang run.

 

octagon-baywindow.dxf -- auto generated DXF CAD file of octagon baywindow drawing each time script is run
octagon-baywindow.pl source code for perl script that generates these octagon baywindow calculations
dxf_header.txt DXF header text file used by this script