DTI vs LTV — The Two Ratios That Determine Your Mortgage Approval
Lenders check both your debt-to-income ratio (DTI) and loan-to-value ratio (LTV) before approving any mortgage. Understand both metrics and where you stand.
Debt-to-Income Calculator
Your monthly debt burden relative to your income
What it measures: Front-end DTI (housing costs / income) and back-end DTI (all debt / income) as a percentage.
✓ Use when
- Before applying for a mortgage or refinance to predict approval odds
- After taking on new debt — to see how it affects qualification
- To find the maximum mortgage payment a lender will approve
- When planning a debt consolidation to improve your ratios
✗ Limitations
- Uses gross income — after-tax take-home pay is lower
- Lender guidelines vary by loan type (conventional vs FHA vs VA)
- Does not account for credit score, which also affects approval
Blended Rate Calculator
Your aggregate interest rate cost across all existing debts
What it measures: The weighted average interest rate across multiple loans — the rate a refinance must beat to save you money.
✓ Use when
- Understanding your current total debt cost before applying to refinance
- Deciding whether to consolidate debts to lower monthly payments (and thus DTI)
- Analyzing which loan portfolio strategy minimizes your blended rate
✗ Limitations
- Does not calculate DTI or predict lender approval
- Rate-focused, not cash-flow-focused
Key difference
DTI measures whether you can afford a new loan (cash flow). LTV measures whether the lender is protected if you default (collateral). Lenders require both to be within limits. Blended rate tells you whether a consolidation would actually improve your DTI by reducing total interest burden.
Worked Example
Scenario
Income: $9,000/month gross. Current debts: $2,100 mortgage + $450 car + $280 student loans + $170 credit cards = $3,000/month total.
DTI = 33.3% back-end (borderline for conventional lending; FHA allows up to 43%). Max mortgage: $2,520/month (28% front-end).
Blended rate on $180,000 mortgage at 7.25% + $28,000 student loans at 5.5% + $12,000 car at 6.9% = 6.92%
Interpretation
The DTI at 33% is manageable but leaves little room. Paying off the credit card ($170/month) would drop back-end DTI to 31.4% — potentially qualifying for a better rate tier.
Bottom line
Run both numbers before applying for any mortgage or refinance. Your DTI tells you if you qualify; your blended rate tells you if the new loan actually saves you money.