Overview
Front-end DTI includes only housing costs; back-end DTI includes all monthly debt obligations. Lenders evaluate both ratios, but back-end DTI is usually the more important constraint for borrowers with significant non-housing debt. Understanding which ratio is your limiting factor directs your improvement strategy.
Front-end vs back-end DTI comparison
| Ratio | Formula | Includes | Target |
|---|---|---|---|
| Front-end DTI | Housing costs / Gross income | Mortgage PITI, rent, HOA | Under 28% (conventional) |
| Back-end DTI | All debt payments / Gross income | Housing + car + student + credit cards + all monthly debt | Under 36-43% |
| Housing expense ratio | Same as front-end | Same | Used interchangeably |
| Total debt ratio | Same as back-end | Same | Used interchangeably |
Monthly gross income $6,000. Housing (mortgage PITI): $1,400. Car payment: $350. Student loan minimum: $200. Credit card minimum: $75. Total debt: $2,025. Front-end DTI: $1,400 / $6,000 = 23.3%. Back-end DTI: $2,025 / $6,000 = 33.75%. Both within conventional guidelines -- this borrower is likely to qualify.
Key Points
- Front-end DTI focuses solely on housing affordability -- how much of income goes to shelter
- Back-end DTI evaluates total debt burden -- the better measure of financial stress
- Most conventional lenders target front-end below 28% and back-end below 36-43%
- If front-end is within limits but back-end is too high, reduce non-housing debt
- If both are high, either increase income significantly or delay the purchase
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Front-End vs Back-End DTI: Understanding Both Ratios
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