One of the best tools available for helping you do the calculations is the minimum payment calculator found at BankRate's website. This tool will allow you to enter in your credit card debt and your minimum payments and it will calculate how long it will take to pay off your card. It will also let you enter in a fixed amount that you can pay each month and it will calculate that for you too.
Here is an example: If you have $2000 in debt on a credit card, 18.5% interest, and the minimum payment is 2.5% of your debt, here is the difference between paying only minimum payments (around $50 the first month) and paying $100 every month until it is paid off.
Minimum Payment: Will take more than 18 years to completely pay off and you will pay more than $2600 in extra interest.
Fixed $100 Per Month: Will take only 2 years to completely pay off and you will pay less than $400 in extra interest.
If you have more than one credit card to pay off, then use this credit card minimum payment calculator instead. The bottom line is that you need to pay more than your minimum payment if you want to save money and eliminate your credit card debt quickly! For more on this topic, check out: Your Guide to Reduce Credit Card Debt.