This is more a recipe than a pattern: you use whichever yarn and needles you want, and knit a hat that will fit regardless of gauge.

Quote from the instructions: “This hat doubles as a tutorial on the Magic loop method. But it also doubles as a gauge swatch, because you can make this hat using ANY weight of yarn with any needles proportionate to that yarn. (If you want to learn Magic loop, or if you want to make a gauge swatch for some yarn you’re thinking of using for big project, your effort won’t be wasted even if you don’t want a hat of this style for your own personal collection. Four oz. of yarn in any thickness pretty much makes a hat, and lots of worthy organizations collect hand knit hats for shivering little kids all over the world.) “