How can I verify the minimum monthly payment number and how it breaks down into principal vs. interest if all I know is the current balance and interest rate?
How can I determine the payoff date of that loan?
1 is pretty easy.
Interest for a month can be calculated by taking your whole interest rate dividing it by 12 and applying it to your balance.
Say your rate is 3.6%.
You divide that by 12 to get .3% interest paid per month. Then take that rate (.003) times your balance (lets say 10000) So your monthly interest is 30 dollars. If you have a 35 dollar monthly payment 30 is going to pay interest 5 is being applied to principle.
for 2 you can use amortization schedules or your can just go to this Existing Loan Calculator which makes it easy for you to compare what adding a few extra dollars to your payment will do to your pay off date.