I have been doing this almost forever in my house turning the flat sheets which my daughter will not use into curtains for her bedroom. I usually will just sew a rod pocket at the top of the sheet, but being that winter is coming I decided to sew these over top of white heavy curtains I already have. They look great with the purple curtains she already had hung.
I started with the Disney Frozen Love Blooms sheet set. It has a very beautiful light purple color to the sheet. My daughter like most of the kids on the planet loves Frozen!
I liked the design at the bottom of the sheet so I decided to measure how long I would need the sheet and cut the fabric that was not needed off at the top of the sheet.
I based the length I would need based on the length of the current curtains (which were staying up) and the two curtain panels I was sewing the sheet to. I then added 1/2" to that length because the sheet will needed to be folded slightly.
Cutting
As soon as I figured out how much sheet could be removed I cut off the excess sheet at the top.
I was left with a 66" x 27" scrap piece I will use to do other crafts like pillows, tie backs, etc...
I then folded the sheet in half and cut the whole length. It left me with two 33" (about) pieces. These will be stitched to the curtain.
Sewing
I folded over the long side that was cut and ironed about 1/4 inch all the way down the sheet to keep it neat while I sewed it. I sewed down the whole length with a sewing machine.
I then folded 1/2 inch at the top and ironed it to keep it neat during sewing. I found the top middle of the curtain and the middle of the sheet lined them up and put a few pins across to keep them together. I then sewed the whole thing across binding the curtain and the sheet together.
I repeated for the other sheet / curtain.
Within an hour I had new curtains that will match my daughters sheet set! Of course she loves them! :)