Debt-to-income ratio, or DTI, is the number lenders obsess over — and it trips up more buyers than credit score does. The good news is the math is simple once you know what counts. Let me walk you through it with real examples.
The basic formula
DTI = total monthly debt payments ÷ gross monthly income, then multiply by 100. Gross income is your income before taxes. The debt side includes the proposed mortgage payment (principal, interest, taxes, insurance, and any HOA) plus other recurring debts.
What counts as debt
- The proposed monthly housing payment (PITI plus HOA/Mello-Roos).
- Car loans and leases.
- Minimum credit-card payments.
- Student loans (treatment can vary by program).
- Other installment loans and certain obligations.
What usually does not count
Everyday living expenses like groceries, utilities, phone bills, and insurance you pay outside of escrow generally are not part of DTI. Lenders focus on debt obligations that appear on your credit report or are otherwise documented.
Worked example
| Item | Monthly amount |
|---|---|
| Gross monthly income | $10,000 |
| Proposed housing payment | $3,000 |
| Car loan | $450 |
| Credit-card minimums | $150 |
| Total debt | $3,600 |
DTI = $3,600 ÷ $10,000 = 36%. This is illustrative only; your numbers and lender guidelines will differ.
Why DTI matters so much
Lenders use DTI to judge whether you can comfortably take on the new payment. In a high-cost market like ours, where payments are large, DTI is often the limiting factor on how much home you can buy — more than the down payment. Managing it is key to approval.
Improving your DTI
- Pay down or pay off high-payment debts like cars.
- Avoid taking on new debt before and during the loan process.
- Document all income sources.
- Consider a slightly lower price or larger down payment.
Frequently Asked Questions
What is a debt-to-income ratio?
DTI is your total monthly debt payments divided by your gross (pre-tax) monthly income, expressed as a percentage. Lenders use it to gauge whether you can afford a new mortgage. It includes the proposed housing payment plus recurring debts like car loans and credit-card minimums. Lower DTI generally helps approval.
Does DTI use gross or net income?
DTI uses gross income — your income before taxes and deductions — not your take-home pay. This is why your DTI percentage may look better than it feels in your actual budget. When estimating, use your pre-tax monthly income. A lender calculates it precisely from your documented income.
What debts are included in DTI?
DTI generally includes your proposed housing payment (principal, interest, taxes, insurance, and any HOA or Mello-Roos), car loans and leases, minimum credit-card payments, student loans, and other installment debts. Everyday expenses like groceries and utilities usually are not included. Student loan treatment can vary by program.
What DTI do I need to qualify for a mortgage?
There is no single universal number; acceptable DTI varies by loan type, lender, and your overall profile, including credit and reserves. Lower DTI generally improves your chances. Rather than rely on a fixed threshold, get pre-approved so a lender can tell you the limit for your specific situation.
How can I lower my DTI?
Pay down or eliminate high-payment debts like car loans, avoid taking on new debt before and during the loan process, document all your income, and consider a lower price or larger down payment. Even paying off a single large monthly obligation can meaningfully improve your DTI and your approval odds.
Why does DTI matter more than down payment here?
In a high-cost market like Simi Valley, monthly payments are large, so DTI often limits how much home you can buy more than the down payment does. You may have enough for a down payment but still be constrained by the monthly debt load. Managing DTI is central to qualifying.
