please don't create incomplete guides like this one here with a misleading formula. what you have found on the internet belongs to many years ago where bitcoin only had 1 type of transactions with 2 type of public keys (compressed and uncompressed)
My bad, I am fairly new in this space and had no idea that fee can vary for legacy and segwit address. Had no idea for more input, I have to pay more fee. I got another thread about future fee of bitcoin transaction and this question peek at my mind that how fee is actually calculated. I was redirected to an article, was probably an old one which had referred to this method only.
Anyway, this is help and beginners board, beginners can do some mistakes. I guess members like you will always help beginners to understand the system, this is why a forum is the best place to learn.
I will update the topic with more information.
Thank you.