DTI = Total Monthly Debt Payments ÷ Gross Monthly Income
The Short Version
Debt-to-Income ratio (DTI) measures how much of your gross monthly income already goes toward debt payments, and it's one of the primary factors lenders use to decide how much they'll lend you (especially for a mortgage) and at what rate. A lower DTI signals more room in your budget to comfortably take on and repay new debt.
Explain It Like I'm 10
Imagine you get a $20 weekly allowance, but $8 of it already goes toward paying back money you owe from before. If a friend is deciding whether to lend you more money, they'd naturally wonder: how much of your allowance is already spoken for? If $8 of $20 (40%) is already committed elsewhere, they might worry you won't have much room left to pay them back too. DTI is exactly that same check, just done formally by banks before approving a loan.
Step-by-Step Example
- 1 Gross monthly income: $6,000.
- 2 Existing monthly debt payments: $600 car loan + $400 student loan + $200 minimum credit card payments = $1,200.
- 3 Current DTI (before a new mortgage): $1,200 ÷ $6,000 = 20%.
- 4 You apply for a mortgage with a projected $1,600 monthly payment. New back-end DTI = ($1,200 + $1,600) ÷ $6,000 ≈ 47%.
- 5 That 47% likely exceeds many lenders' comfort threshold — you might need a smaller mortgage, a larger down payment, or to pay down some existing debt first to qualify at a reasonable rate.
Someone with $6,000 gross monthly income and $1,800 in total monthly debt payments has a 30% DTI.
Quick Recap
- ✓ 'Front-end DTI' considers only housing costs; 'back-end DTI' considers all debt payments (housing, car loans, student loans, credit card minimums, etc.).
- ✓ Mortgage lenders commonly look for a back-end DTI below roughly 36–43%, though exact thresholds vary by lender and loan type.
- ✓ DTI is calculated on gross (pre-tax) income, not take-home pay, which can make the ratio look more favorable than your actual monthly cash flow feels.
- ✓ Paying down existing debt (even without earning more) directly improves DTI and can improve loan terms available to you.