First Ever Hat Design Under Way

This strange looking creature is the beginning of a hat, which I’m having a go at designing.
I’m using some basic instructions from Debbie Abrahams’ “Design your own knits”.

This book is very good, but it will say something like “calculate the number of rounds you need to knit for the depth of the hat”, but doesn’t actually say how to calculate this.
Yes, if you know the distance and the guage, you can calculate it, but not if you don’t know the recommended distance.
This sort of thing happens again and again in this book. “Calculate the number of stitches for the width of the back neck and the shoulders”, but the body measurements for these distances are not mentioned. Is it from shoulder point to shoulder point? I’m battling on, but it does seem a bit like it’s written for those who already know how to do it.
I suppose it’s not “Design your own knits for dummies”.

I pored over the page on hat design over and over again looking for information about the recommended amount of negative ease. I gave up looking and guessed, and then when following the steps, one by one, there it was, in black and white, right in front of my eyes.
5cm (2 in). Sadly, this sort of thing seems to be a common occurrence for me lately.

I’m having a look at the Vogue Knitting “The Ultimate Knitting Book”, with a view to perhaps using it for vests, pullovers etc.
I do tend to skim over pages looking for key information, rather than methodically reading through each part. I must learn patience in this area.

Since taking this photo, I’ve actually finished knitting the hat, but haven’t yet taken another photo. I don’t know if I want it photographed on my ugly head though. I may have to recruit one of my daughters.

It uses the tulip stitch pattern for the bottom of the hat, and reverse stocking stitch for the top.

I’m really pleased with it, for a first attempt. I plotted out the curve of the decreases on graph paper, but it does seem a bit like a star at the top, though not when it’s on my head.

I can’t find standard measurements for crown of head to forehead or base of skull. Circumference is easy enough to find. All of this is fine when designing for oneself, but if designing for others, what are these measurements for baby, child, woman, man?
The list of questions is endless. Persistence is the key.