Guide
What is DTI?
Debt-to-income is a percentage: how much of your gross monthly income is already spoken for by housing and other recurring debts. Mortgage files almost always show two versions of that percentage.
DTICheck is an educational estimate. It is not lender underwriting, a pre-approval, or credit advice. Conventional 28/36 and FHA 31/43 are widely published guideline bands; actual overlays and automated findings differ. Read the full disclaimer.
The two formulas
Front-end DTI, also called the housing ratio, is monthly housing cost divided by gross monthly income. Back-end DTI, also called the total or backend ratio, adds other monthly debts to housing before dividing.
Example: $8,000 gross income, $2,000 housing, $400 other debts. Front-end DTI is 25%. Back-end DTI is 30%. Run the same example in the calculator with?income=8000&housing=2000&debts=400.
What counts as income
Published mortgage DTI uses gross monthly income — pay before income tax, 401(k), and most other paycheck deductions. W-2 wages are the simple case. Overtime, bonus, commission, self-employment, Social Security, and rental income may count when they are stable and documented. A calculator cannot see tax returns; a lender will.
What counts as housing
For a purchase or refinance, housing is the proposed monthly payment: principal and interest, property taxes, homeowners insurance, mortgage insurance if required, and HOA or condo dues. Do not stack your current rent on top of the new payment unless you will keep that rental.
What counts as other debt
Back-end DTI usually includes auto loans, student loans, credit card minimums shown on the credit report, personal loans, and court-ordered support. Utilities, groceries, childcare that is not a loan, and subscriptions normally sit outside DTI even though they still hit your budget.
Student loans are a common mismatch. Some programs use the credit-report payment; others use a percentage of the balance when the payment reports as deferred. If your result and a loan officer’s worksheet disagree, ask which student-loan rule they applied.
Why lenders care
DTI is a capacity test. Credit score speaks to past payment behavior; DTI asks whether the new payment still leaves room for other obligations on paper. It is only one part of a file. Reserves, down payment, property type, and employment history can move a decision even when DTI is the same.
For typical published bands, see good DTI for a mortgage. For ways to change the ratio before you apply, see how to lower DTI.