Today, I made this cute headband out of an old knit-fabric dress! I didn't have to use elastic because the dress already had some stretch to it. All you need is an already made headband (or the circumference of your head), an old knit dress (you can find one of those at the thrift shop), some scissors, a pencil and a sewing machine.
Step 1: Finding the right size
First you need to cut up your knit dress, so you have a long strip. Since you'll be cutting on the bias of the dress, make sure it's wide enough. Grab a headband (you'll notice I'm using the one I crocheted here) and draw a line around it, making sure it's doubled in both width and height, like the picture above. Make sure you're doing all of this on the bias of the dress, so it will be able to stretch.