My hat measures approx. 11’’ in circumference and fits my cat approx. 10 lbs and dog approx. 14lbs

Depending on your size of dog/cat you could probably go up or down a hook size to adjust it to fit.

On round 1 for the hat, you can easily ch 37 and hdc in the second ch from hook and in each ch st around instead of the fhdc but the fhdc will stretch more.