Bias tape is fabric that is cut diagonally to the grain of the fabric and then has each edge folded in to meet in the middle. It is commonly used to finish edges of bags, shirts and many more projects.
The difference between a straight (with the grain) cut and a bias (diagonal to the grain) cut is the bias cut has much more stretch to it. Only woven materials will have a different elasticity to different cuts, felt and interfacing materials are not woven and do not have a bias. Information courtesy of Wikipedia.
The first step to making bias tape is to cut strips on a diagonal out of your fabric that are double the size that you would like your tape to be, so if you want 1” bias tape, cut 2” strips of fabric (Bias tape is measured after the edges are folded into the middle, but before the tape is folded in half to fit around the rough edges of the project). 1” bias tape will be folded to ½” on each side of the finished project.
Join your strips of fabric together by placing two strips right side together at the edges, with them overlapping like so:
Sew them together, as shown in the photo below. Trim the excess off. Attach as many strips as needed.
Press the seams flat.
Next, fold the edges in so they meet in the almost in the middle, with one side a little larger than the other.
You can make the folds by hand or by using a bias tape maker. If you want to make the tape by hand, start at one end, and fold in the edges to meet slightly off the middle. Press. Pin the end of the tape to the end of your ironing board and continue to fold in the edges and press along the length of your fabric strip.
Using a bias maker, insert the fabric in the big end of the maker, pull out a little bit of the fabric, iron the folds down, pin the tape to your ironing board. Begin to pull the tape maker and press the fabric that comes out with folds already made. Continue to the end of the fabric strip.
To store bias tape that you are not going to use right away, wrap it around a piece of cardboard, a paper towel roll or an extra spool.
Quick note: I learned how to make bias tape from the instructions included with one of my bias tape makers made by Unique.
If you are planning to make a lot of bias tape all the time, you can also invest in a bias tape machine. All you need to do is create the strip of fabric, place it in the machine and it folds, presses and spools the tape for you.