If you ride a bike you may have seen the shirts some serious bike riders wear with one or more pockets on the back. My bike-riding partner was going to buy one of these shirts so she would not have to wear a backpack to carry a few personal items (I happen to know she carries snacks). I looked at a few of these shirts and decided that adding a pocket to a t-shirt would be easy. After all, it is just the front half of a zipper bag that is edge-stitched to the back of a shirt.

Supplies:
Shirt to which you want to add the pocket
Scrap of fabric big enough to hold what you want to put in the pocket
Nylon zipper

Instructions:
The measurements I am using are for a finished size of approximately 6” x 10”. Remember, this is your pocket and you can make it any size you want.
1. Cut lower-front pocket fabric 6” x 11”.
2. Cut upper-front pocket fabric 1 1/2” x 11”.
3. Cut two pieces of fabric 1 1/2” x 3”
4. 12” nylon zipper.

5. Place 1 1/2” x 3” fabric and one end of the zipper right-sides together with the zipper stop at the center of the fabric rectangle. Sew across the long part of the zipper 1/4” from the zipper stop. This will prevent the zipper pull from coming off when you cut off the zipper stop. Repeat on the other end of the zipper.
6. Trim off one end of the zipper, removing the metal stop.
7. Turn zipper right-side up.

8. Fold fabric wrong-sides together at the stitch line.
9. Trim fabric 1” from fold line.

10. Trim fabric even with edges of zipper tape.
11. Repeat Steps 6 to 10 on other end of zipper.
12. Layout the three sections of your pocket in the order you are going to assemble them.

13.  Place zipper right-side down on the right-side of the lower fabric section. Put a zipper foot on your machine.

14. Carefully sew the pieces together. To avoid hitting the zipper pull, move it out of the way when the zipper foot gets close to the pull. To do this, place the needle in the down position and raise the presser foot. Carefully move the zipper pull tab to the backside of the foot. Make sure the  fabric is lined up straight with the zipper foot again and lower foot to continue sewing to the end.

15. Place zipper right-side down on the right-side of the upper fabric section. Repeat Step 14 with the top fabric section.
16. Press fabric away from zipper teeth.
17. Top-stitch from the right-side along both sides of the zipper.
18. Press the edges under 1/2” on all four sides.
19. Set the pocket front aside.

20. Prepare t-shirt by folding in half to find center back.
21. Mark where you want the bottom of your pocket. I noticed that the lower edges of bike shirt pockets tend to be located just about waist level.
22. Using a fabric pen, mark where the lower edge of the pocket should be.
23. Mark the center line of the t-shirt.
24. Match the center line of the pocket with the center line of the t-shirt and the bottom edge of the pocket with the bottom edge line.
25. Pin the pocket in place and edge-stitch around all four sides. Your pocket is complete.

Comment on my original design: For the first pocket I made, I did not put fabric strips on the ends of the zipper (see photo below). I prefer the way the pocket looks with fabric at the ends of the zipper tape. If you prefer the look in the photo below, you can omit the zipper end fabric pieces.