Double the width has worked for me for a straighter, un-bunched look. Shirred curtains do better 2.5 x the width. 3 x the width would be a bit much for any application, IMO.

Thick and heavy drapery fabric is best at 2x fullness or slightly less. I did my LR and DR draperies at 1.5x - 1.75x fullness because of the fabric bolt widths. But the fabric was of heavier weight, so the draperies turned out just right - not too bulky, but not skimpy either.

My mom and I made the sheers/light cotton curtains in other rooms at 2x fullness, and it was just right.

Thank you for the feedback! I'm feeling much better about the 2.0. I actually don't want that heavy, full look, but was concerned I was going to end up with skimpy. Sounds like the 2.0 is perfect. The fabric is a drapery fabric - not sheer and not upholstery weight. Thank you!

Kim: Are these stationary panels? How wide are the windows? The wider the window, the fuller the drape.

Ratherbesewing, my living room window is actually 3 windows 11 feet wide. I'm putting stationery panels on each side. Since there is only 6" of wall space and I don't want to cover too much window space, these panels are 20" total. 108" tall.
My dining room has 2 windows 6 feet total. Again, I'm doing stationery panels left and right. 24" panels but there is plenty of wall space so they won't block the window. 132" tall.

I don't know if you ever knew Rhoda (Georgiagal) who used to post here and has a very popular blog - but she recently moved and had stationary panels made for a couple of rooms. I asked her about them because I have been thinking about using the workroom she used. She did pleated panels and they are only the fabric width. But - she is like you - wanted stationary and did not want much window space covered.

I'm linking her blog and you can take a look.

tina

Here is a link that might be useful: southern hospitality blog