Get a better understanding of how credit cards work, including how to manage credit cards, in this free lesson.

If you want to determine the finance charges on a product or service you might purchase with a credit card, enter the cost, interest rate, and payment. For example, how much does that $700 stereo system really cost at an interest rate of 15 percent?

It can be amazing what a difference an interest or payment amount can make in how much you end up spending.