Making minimum payments on your credit cards could cost you — big. And a new tool will show you just how much.

The website ReadyForZero created a calculator that assumes an annual interest rate of 15 percent, and then it totals up the final cost of your debt and how long it’ll take you to pay it off. The results can be not only eye-opening, but frightening.

Example: if you make minimum payments on a debt of $3,000, it’ll take you 17 years, four months and one day to zero it out. And along the way, you’ll pay $3,174 in interest — meaning you’re essentially paying more than twice what you originally owed.

Experts say making payments even slightly above the minimum due can dramatically reduce the payment duration and the final amount you end up shelling out in interest. Or, best of all, don’t charge anything you can’t pay off at the end of the month.