This calculator will show you how much interest you will end up paying if you make only the minimum required payment on your credit card bill -- that is, assuming you stop charging any more to it. After seeing the shocking figures this calculator will generate, I doubt you'll want to continue allowing the credit card companies to build your swimming pool in their backyards. And as you will see from the calculated results, it's not just the interest charges you're losing, you're also losing the interest you could be earning on those charges if you were investing them rather than paying them to the credit card company!
Somewhere in your credit card disclosure statement the card company will tell you something like "your minimum payment will be 2% of the balance or $10, whichever is higher." These are the figures you will enter in Row #3 and Row #4 respectively.