I checked the measurements as I did the increases since I was working at a different gauge - as it turned out, working up through round 10 (size small) worked for making a size medium at the gauge I was getting. It relaxes a little with washing, so if you want a snug fit, you may want to go with something that feels a little tighter than you want the finished hat to be if you are trying it on as you go. I also made this a little longer, both to be slouchier and to fit in a few more stripes - it’s fun to keep crocheting and seeing the new colors come up!