This will help!
I match up the corners lengthwise and fold one inside the other. Then again width. Lay down and fold down the two sides that have a gathered corner. Then I fold my flat sheet the same size and lay on top of the fitted. Next is pillowcases. Then fold all of them twice (once each way) for a tight square. Some people like to keep one pillowcase and put the set inside.
Fitted sheets are evil! No matter how hard I try to fold one, I end up rolling it into a ball and stuffing it in the linen closet. My wife is not pleased.
From other Hometalkers.
here's a bunch of videos how to https://www.youtube.com/results?search_query=diy+folding+fitted+sheets