* The Extra Cost (E) is the lump sum of all extra costs involved in the loan, which include points, application fee, closing cost, processing fee, title fee, and so on. In short, it's the money you borrowed that you never saw.
This calculator first calculates the monthly payment using C+E as the total loan amount:
where r is the adjusted equivalent interest rate applied to the total loan amount C+E
The APR is essentially the actual interest rate applied to the intended loan amount C and can be calculated iteratively by solving the following equation using the Newton-Raphson method:
The annual percentage rate A is calculated using the following formula: