Credit card debt takes a toll. Beyond the stress of having it hanging over you, the interest can cost hundreds or thousands of dollars per year. According to a new NerdWallet study, the average U.S. household with revolving credit card debt — balances carried from one month to the next — incurs interest charges of $904... More From NerdWallet How is credit card interest calculated? How to stop wasting your money on credit card interest Does your credit card’s interest rate matter? Erin El Issa is a writer at NerdWallet.