Article: While amortization math is fairly complex, you should at least get a handle on it so you understand how the calculations work. However, you don't have to do every calculation by hand – you can use an online calculator.  To start, you'll need the following figures: the initial principal or amount of the loan, the interest rate per period, and the total number of payments or periods. Add one (1) to the interest rate to period, then raise this sum to the power of the total number of payments or periods. Multiply this figure by the interest rate per period, and place this number on the top of a division symbol. On the bottom of the division symbol, take the figure you got when you added one (1) to the interest rate and raised it to the power of the number of payments, then subtract one (1). Complete the division and multiply that amount by the initial principal to find the payment amount per period. There are many independent financial websites that have amortization calculators available. Banks and other lenders also often have these calculators available on their sites. If your lender has a calculator available on its website, you may want to use that one as opposed to one offered elsewhere. Not that there's going to be much, if any, difference in the calculation, but using your lender's calculator gives you a little more ground to stand on if you find a difference between the monthly payment you calculated and the one your lender calculated. Online financial calculators provide spaces for you to enter the total amount of the loan, the term of the loan, and the annual interest rate. There also may be places for you to describe the type of interest or enter any fees. Once you've provided the necessary information about your loan, the calculator will provide you with the amount of your monthly payments so you don't have to do all that math by hand.  Keep in mind that amount you calculate may be different from your actual monthly payment if your lender charges fees that you left out of the calculations. For example, if you have a $150,000 mortgage with an annual interest rate of 4.5 percent and a loan term of 360 months (30 years), your monthly payment would be $842.50. If you have a car loan for $30,000 with an annual interest rate of 5.25 percent and a loan term of 60 months (5 years), your monthly payment would be $569.58.

What is a summary?
Learn the monthly payment formula. Find an online financial calculator. Enter the terms of your loan. Determine your monthly payments.