There's a much easier solution: use
https://coinb.in/#fees, and in a few clicks you get the size including a recommended fee for a fast transaction. Note that most transactions don't need to be
fast.
Yes this site made me people lazy LOL (especially me). Until today I did not have this mind how byte size calculation works. All those days I only played with the sat/B field.
Thanks OP. It was useful more me 🙂 I left you some reward. Enjoy your 50 merit mark.