Get two 40” panels per window. Hang a rod WIDER than the window trim so that the panels can be pushed open to expose the entire window glass. Most of the panel fabric will be hanging in front of wall, not window.

Do you want 'curtains'--with a rod pocket? Or 'draperies' --with pleats?

Fabric should be a skimpy two to one up to a custom three to one ratio of fabric to rod width. plus add 'repeats' if drapery panels meet and overlap in the centers. Plus fabric for 'returns' at the outer edges to cover side gaps between rods and walls.

There should be charts to figure out how wide a rod is needed to extend beyond the glass so you can draw open the panels and have all the glass showing.

These types of curtains will require a lot of extra overhanging rod, so figure out how much space you have adjacent for the roof before you decide. I just had to return some back tab curtains due to how wide they were when pushed back. You have a bit more leeway with decorative curtains. Even though you're supposed to make them look like they can close, for rod pocket types I think going a bit less than recommended is fine.

For context the curtains in my living room and dining room are just aesthetic and I used fewer panels than would be required to close because of how much space they took up on the rod.