THE NUMORIX GUIDE
How to use the Debt-to-Income Ratio Calculator
Last reviewed September 14, 2026
What this calculator does
The calculator normalizes income and debt inputs to monthly values according to salaryMonthly and debtsMonthly, then divides housing costs by monthly income for front-end DTI and all debts by monthly income for back-end DTI.
Formula and method
The calculator normalizes income and debt inputs to monthly values according to salaryMonthly and debtsMonthly, then divides housing costs by monthly income for front-end DTI and all debts by monthly income for back-end DTI. Housing includes rent or mortgage, property tax, HOA, and home insurance; other debts include cards, student, auto, and other loans.
Variables and inputs
Income fields are salary, pension, investment, and other income. Debt fields are rental cost, mortgage, property tax, HOA, home insurance, credit cards, student loan, auto loan, and other loans. The input type also has switches for whether income and debts are monthly; the current UI defaults both to monthly and does not expose toggles.
Worked example
With $6,000 monthly income, housing costs of $1,500 mortgage + $300 property tax + $100 insurance = $1,900, and other debts of $200 cards + $300 student loan + $400 auto loan = $900, total debt is $2,800. Front-end DTI is 1,900 / 6,000 x 100 = 31.67%; back-end DTI is 2,800 / 6,000 x 100 = 46.67%.
How to interpret the result
Front-end DTI isolates modeled housing cost; back-end DTI includes all listed monthly debt. The labels Good, Caution, and High compare the result with the route's 28% housing and 36% total reference limits, not with every lender's underwriting policy.
Common mistakes to avoid
Use gross income and consistent periods. Do not enter annual salary while the monthly switch is on. Include required debt payments rather than balances, and do not leave property taxes or insurance out just because they may be escrowed.
Assumptions and limitations
The current UI uses monthly defaults and does not expose the period switches. Qualifying-income and debt definitions vary by lender, and this route omits credit, reserves, loan type, irregular income, and non-listed obligations.