Both of the Ravelry patterns that you have said are similar are pillbox hats, but they are worked in different ways. The Knotted Pill box is worked as a straight tube from the botom up, then after a welt is worked is knitted flat on the crown. The Garnstudio hat is worked as a flat cabled band, which is then joined in a circle and stitches picked up for the flat crown to be worked.
It would be hard for someone to do the math for you, as it will vary depending on yarn type, size, and patterning. You could work up a hat without really doing much math by using the method of the Garnstudio hat - make a strip as wide as you want with whatever patterning you like long enough to fit around your head, then join or sew it in a circle and pick up stitches on one side and knit a flat crown inwards. The method to get a flat cirle while decreasing is to decrease 8 times evenly spaced every other row (that's the extent of the math you'll need). When you get down to less than 16 stitches just knit 2 together around and pull the end through the live stitches to close.
I would knit the hat at a sturdy gauge so that the band holds it's shape. Hope this helps, good luck.