Qualification metric
What DTI Ratio Means
Debt-to-income ratio, or DTI, compares monthly debt obligations with gross monthly income. Lenders use it to judge repayment capacity, but a lender's maximum is not always the same as a comfortable household budget.
Quick Take
- DTI is monthly obligations divided by gross monthly income.
- Mortgage underwriting generally counts the housing payment plus other recurring debts.
- A lower DTI leaves more room for repairs, savings, and life changes.
The basic DTI formula
DTI equals monthly debt obligations divided by gross monthly income. If monthly income is $9,000 and total monthly debts after the new mortgage are $3,150, the DTI is 35 percent.
The numerator can include the new mortgage payment, taxes, insurance, mortgage insurance, HOA dues, car loans, student loans, credit-card minimums, leases, alimony, child support, and other recurring obligations.
Front-end vs. back-end DTI
A front-end ratio looks mainly at housing cost. A back-end ratio looks at housing plus other debts.
The back-end number is usually the better stress test because a mortgage does not replace car payments, student loans, or credit cards.
Lender limits are not comfort limits
Fannie Mae guidance describes different DTI thresholds depending on underwriting path and borrower strength. That does not mean every household should borrow up to the maximum.
A buyer with irregular income, older vehicles, a large family, medical costs, or limited savings may need a much lower DTI to feel safe.
How to use DTI in planning
Run affordability at a conservative DTI first, then compare the result with the maximum your lender discusses. The gap is useful: it shows how much room you are choosing to keep or give up.
If the desired home only works at an aggressive DTI, model repairs, taxes, and insurance increases before making an offer.
Run the numbers