Hat shown is a ladies xsmall/small size. This hat is knitted in the round. To make hat larger while maintaining pattern, you would need to cast on more stitches in more stitches in multiples of 16 stitches.

Stitch patterns used in this pattern are mentioned in the Pattern Post here:
http://smariek.blogspot.com/2006/12/swirl-hat.html
and also in the Pattern Bibliography post here:
http://smariek.blogspot.com/2007/11/pattern-bibliography.html
.