Based on a head circumference of 21” (53.5 cm). Diameter to stop increasing is calculated as such:

Head circumference divided by 3.1415 (pi) (example: 21”/3.14 = 6.68”)

This pattern uses crossed dc in the round within the first six rounds but I have included an easier alternative for the crown (rounds 1 to 6). It is not difficult but can be challenging in terms of focus and counting. The actual pattern is in the body of the hat and is straight forward.

The pattern is for a beanie but can also be converted into a slouchy version.