Mortgage calculator with multiply interest rate

getmore4less

With any calculation comparison you can only go as far as the fixed data points anything beyond those is into speculative guessing so in most cases you need range based calculations so no body bothers.

comparing fixes with the same initial term you only need to go as far as the fixed terms and see what you owe. after that it I the more speculative factors like does a lender do good retention deals.

The time you do need to do more calcs is comparing things like a 2y+ follow on options against say a 5 year rate . with that you can work out what the rates would be if you did say a 2+3 or a 5, you can calculate what the 3y follow on must be to break even so you can assess against a guess of future rates.

ComputeAngel

This should serve your purpose
https://forums.moneysavingexpert.com/discussion/1157173