For example, if you pay $ 3000 a month for your mortgage (escrowed and HOA added) and another $500 a month for an auto loan and $400 a month for the rest of your debts, your monthly debt payments are $3900. ($3000 + $500 + $400 = $3900.) If your gross monthly income is $12,000, then your debt-to-income ratio is 33 percent.