 Credit card debt fell slightly in April, but it bounced back the following month. The Federal Reserve's measure of revolving credit, which includes credit cards, grew at an annual rate of 6.3% in May. WalletHub, which tracks credit card spending, estimates that Americans are now carrying a balance of more than $1.25 trillion on their cards. For those who pay their balance in full every month, that's merely a convenience. For others, it's a costly form of debt. The average interest rate on balances carried over from month to month is nearly 23%.