How do I change up this baby crochet pattern for bigger sizes?

I foudn this adorable crochet pattern for a babby hat, it's made by making the length and then joining it to the other side of the rectangle and doing a circular stitch around the top decreasing by one in each row. it's one of those baby fruit hats (pumpkin, apple, blueberry, etc.) The pattern is for new borns, 0-3 mo. That is 25 rows of a Double half crochet. Even that seems tiny for a newborn once done, i mean, a NEW NEW born. Maybe a preemie. I would like to make it in different sizes, but I don't know what the width is for different age babby hats? if that makes sense... So if anyone knows how to go about this, or knows a better (and free) pattern for it, please give me your input.