My gauge:

hslst 16 st = 4 inches
18 rows = 4 inches

I could not meet gauge no matter what hook size I used. I used size J as that is the closest I could get to the pattern’s gauge. Going up to size K I had too few stitches and it made the cowl too loose/floppy. I had to compromise and go with size J, which gave me the closest stitches per inch. I adjusted the length by doing an extra repeat at the end before seaming so it would fit over my big head and thick hair.