I crochet hats for my kids every year. And while I may use the same yarn, I probably never use the same combo of hook and yarn. So I end up making the same hat about 5-6 times before it's finally the correct size. It's getting frustrating especially now that they are old enough to be opinionated and want to have multiple colors of hats made of different thicknesses of yarn. Is there a guide somewhere that will tell me that if the kid's head is X inches around you need a diameter of Y...that way I can just measure the darn thing at that point and not have to do another dozen rows to then find out it's too big or too little and have to frog it back?