Folding a fitted sheet is considered by many to be a magical cleaning secret that only Martha Stewart can pull off. But it's not really that hard, once you know how (and practice a few times).
The reason why fitted sheets are so darn hard to fold is that they have stretchy, rounded edges. It's obvious how to fold a square object, but a rounded one is a little tougher.
I've seen a lot of tutorials online about how to fold a fitted sheet, but I've found a fool-proof way that's a little less complicated.
Do the prepwork
First, lay the sheet out on a flat surface like your bed or the floor. Then, grab one edge and tuck it into the edge directly across from it.
So, if I grabbed the right edge, I want to tuck it into the left edge. It doesn't matter if you're tucking horizontally or vertically -- just don't tuck diagonally. Also, as you tuck, be sure to make the corner seams line up.
If you do this part right, the elastic will be folded down and the new edge of the sheet will be smooth right angles. Do the same thing to the bottom corners.
You can breathe a sigh of relief: The hardest part is over. Just smooth out the edges and corners. If the sheet won't lay perfectly flat, don't panic. The bumps will be hidden by the time you finish folding it.
Now you should have a rectangle (-ish) shape to work with. Fold the sheet in half so that the elastic edges are hidden. Smooth out the corners and fold the sheet in half, again. Keep folding it in half until you have a nice, neat bundle.
This will probably take some practice to get the hang of. It definitely took me a while.
Shortcut bonus tip
There is another way. You can just fold your sheets however you want, then stuff them into a matching pillow case. Your linen closet will still look tidy and no-one will ever know.