I know this is an old thread, sorry about the necro bump, but hope to improve accuracy of information…
Not to disagree, but the basic rule for CoreXY is twice around the area.
The belt travels both length and width of the area twice, so it’s 4X length + 4X width.
Tallying lengths (L) and widths (W) as follows:
Magnet to carriage (0.5W)
Carriage to alpha motor (0.5L)
Alpha motor to corner (1.5L)
Corner to corner (1.5W)
Corner to carriage (2L)
Carriage to Carriage, attaching to magnet on the way (2.5W)
Carriage to beta motor (2.5L)
Beta motor to corner (3.5L)
Corner to corner (3.5W)
Corner to carriage (4L)
Carriage to magnet (4W)
Total belt length is 4L + 4W give or take a bit.
Hmmm. I have 5M of belt, I might not have enough for the planned table size.