My hats from last row of ribbing are six inches until I start the decreases. Using WW yarn, I start with a CO of 88 sts, knit edging/ribbing and the tube. Then knit six sts, k2tog repeating around. Then a round of even knitting. Then knit 5 sts, k2tog around, then even and follow the pattern of decreasing until there are about 4-12 sts depending on how tired I am or how thick the yarn is.
This pattern can be adapted for any yarn or size head. The CO is in mutiples of 11. I've made several out of different kinds of yarn and they've all turned out great and fit perfectly.