loan calculation formulas

How can I calculate my car monthly payment - at the dealership?

Where can I find a amortization chart, or a formula for my calculator to take to the dealership if I have to use their financing (I have a 5 year old bankruptcy)

They will rip you when they start asking what you want your monthly payment to be - for me it is the interest rate and amount of time for the loan. I need to be able to calculate this stuff based on interest rates they will give me - there at the dealership. so I wont have my computer to do calculations automatically.

Amount of the car, meaning less your down payment.
Divide by terms, add interest, equals your monthly.

Example:

Principle + interest divide by loan term less down payment. You should be able to come up with your minimum monthly payment. Ofcourse, the longer you have the loan the smaller your monthly is going to be.