Loved Anchie's analitical breke down. Will think about how das it implement by me when having more time.
But thought I will give also my 2 cents learned from Suz, years ago here on YLF.
She was the first to aknowledge that she cannot really devide her wardrobe in simples and equals of 4 seasons, because she had changes in weather rather each 6 weeks of the year. That's my approach from then on. So for ex. Spring is 12 weeks here but devides in cold spring and warm spring for me- so I rather concentrate on capsules worth of 6 weeks. Same with each other season.
Then, I had to decide how many completely different outfits can I include in a mini season per each of my lifestyle's need (work, casual, lounge, dressy..)-and how many times I am willing to repeat each outfit during the 6 weeks. When deciding on outfits I'd also taken account my preffered silhouettes- and then decided how many of these outfits should include pants, skirts or dresses. Then split them down from there even more---just like Anchie started with (neutrals, colors, exact and more speciffic pieces I need, etc)....you get it.
This is only for an approximate math. I am not following it strictly but for me was a good starting point.
Laundry bottlenecks count, too. I have a large wardrobe, and now I can go 2 weeks without major laundering which I treasure a lot -as so I don't have the laundry stress and also got free time to do something else instead each other week ---but guess, each has to decide on it' s own.