Debt-to-income ratio is the ratio of all personal debt — including credit card debt — to gross personal income. For consumers, debt-to-income ratio comes into play when they attempt to qualify for loans. A high amount of credit card debt can force a consumer into paying higher rates on a mortgage, or could even cause it to be denied. Debt-to-income ratio can also come into play for entrepreneurs trying to start businesses by affecting their ability to get loans.