I have found all kinds of calculators that can do this work for me to calculate student loans, but I am curious about the actual formulas that it takes to get these answers. Most private loans are variable rate, but I am trying to find something that will help me figure things out as close as possible.

What is the value of the loan after the deferment process when payments begin if interest is compounded monthly?

How much will my monthly payments be?

How much interest will be paid by the end of the loan?

I'm not sure if this is enough information, this process is so confusing.