I was at a crafts market and saw all these cute infinity scarfs and decided to try to make one on my own. I ordered tons of fabric and after a test run, I started with the first scarf. It's actually quite simple and fast, I make one in about 2 hours. Since christmas is coming closer, and I realized I really like making these, I will now make them as x-mas presents for my friends and some of my family.

All you need is:

2 pieces of different fabric, you can also take the same, but the effect is much nicer with two different ones. I usually take one piece with a pattern (with animals, or bikes, or stars) and one unicolored with a color that can also be found in the pattern, like the pink in the cats.
A sewing machine and color matching thread
Needle for the last piece of hand-sewing

Step 1: Cut the Fabric

Cut both fabrics to approximately 26.5 cm x 150 cm (10.5 inches x 59 inches). You can also make it longer (so you can wrap it around your neck 3 times instead of only 2 times). I would not recommend to make it narrower, since it doesn't fall so nicely around your neck otherwise.

Step 2: Sew the Two Pieces Together

Lay both pieces on top of each other, so that the "nice side" is facing inwards
Pin the pieces together along one LONG side
Sew this side with a normal stitch I took a regular straight stitch like this: ------------
Flatten the fabrics with your hand and sew the other LONG side (I did not pin this side again, since I am lazy :) and it's not necessary when you sew carefully.

Step 3: Invert the "almost-scarf"!

It's important you invert the scarf BEFORE you start sewing the short sides! That's why I put it as a seperate step! Now you should have the nice sides of the fabrics outside.

(I actually tried inverting it AFTER sweing half of the short sides in my first version but after inverting it ended up in a cylinder instead of the donut I expected. Must be mathematically explainable but I couldn't figure it out (so if anyone has an Idea why, let me know!)

Step 4: Sew the Short Sides

"Inside sewing": Arrange your scarf such that the two short sides touch each other (see image). Then, grab it at the transition of both fabrics (see image) and start sewing from there. Don't sew all the way through (it's anyways not possible) but stop when the opening becomes too narrow. I would recommend to leave the opening on the unicolored part, since this will be the part less visible later.
Turn the part that you sewed around and sew the opening by hand.

Note: When you do this "inside sewing" for the first time, it might feel a bit akward but just continue and then after inverting this part, you will see how it all works out.