Your debt-to-income (DTI) ratio is your total monthly debt payments divided by your gross (pre-tax) monthly income. Lenders lean on it to judge whether you can actually carry the mortgage you are asking for.
There are two flavors:
- Front-end DTI — just the housing payment (principal, interest, taxes, insurance) as a share of income.
- Back-end DTI — housing plus everything else: car loans, student loans, credit card minimums, and other obligations.
The classic guideline is the 28/36 rule — housing under 28% of gross income, total debts under 36% — though many loan programs allow higher back-end ratios when you bring compensating strengths like cash reserves or excellent credit.
If your DTI is tight, you can lower it by paying off a small loan or card before applying, or raise the income side with a co-borrower. See DTI ratio for a mortgage for target numbers by loan type, then sanity-check the whole budget with how much house can I afford.