I am not giving you any measurements --- just guiding you through what I did to make them.
I did not want a binding edge like this cap had, so I doubled the size of it and folded it in half.
Marked with the pins some halfway points for lining it up.
and on the strip too.
Pinned to make a few gathers and eased the rest of it.
I used the point of my scissors to make little tucks in the cap part. I know I could have stitched a basting stitch and pulled it, to gather it, but there's only a little gathering to do on the top of the cap.
I stitched from the end to the center and then turned it around and stitched from the other end to the center.
I could have serged or zig zagged the raw edge, but I didn't as it will only be used for a couple months and it will wash up just fine! If I were making it to sell, I would have finished the raw edges.