Average credit card balance $6,678: the monthly cost of carrying the record debt

The average credit card balance in the United States rose to a record $6,678 in the third quarter, according to TransUnion's quarterly Credit Industry Insights Report. Carrying that balance at the average all-account APR of 21.19% tracked by Federal Reserve data costs about $118 a month in interest before a cent of principal is paid. That monthly load, not the headline total, is what makes this quarter's record card debt a cost-of-living story.

The average card balance hit a record $6,678 in Q3, up 9.7% year over year. At the 21.19% average APR, that balance costs about $118 a month in interest before principal. Card balances total a record $1.29 trillion; HELOCs saw their largest quarterly j…