“My credit score is in the high 700s, I’ve never missed a payment, and the lender still told me I could borrow less than I expected. What else are they looking at?”
Very often, the answer is your debt-to-income ratio, or DTI. Your credit score tells a lender how you’ve handled debt in the past. Your DTI tells them whether your income can carry one more payment right now. For mortgages especially, a great score can’t rescue a DTI that’s over the limit.
The formula is simple; the inputs are not
The Consumer Financial Protection Bureau defines DTI as all your monthly debt payments divided by your gross monthly income. Gross means before taxes, retirement contributions and health insurance come out of your paycheck.
Take a hypothetical borrower earning $78,000 a year, or $6,500 a month gross, who is applying for a mortgage:
- Car loan: $450
- Student loan: $300
- Credit card minimum payments: $120
- Proposed mortgage payment, including taxes and insurance: $1,900
Total monthly debt is $2,770. Divided by $6,500, that’s a DTI of about 42.6%.
What counts as debt
Lenders count recurring obligations that show up on your credit report or in your legal paperwork: mortgage or rent on the new home, auto loans, student loans, personal loans, minimum credit card payments, child support and alimony you pay. If you cosigned someone else’s loan, that payment usually counts against you too, even if they make every payment.
What generally doesn’t count: utilities, phone bills, groceries, car insurance, subscriptions and other living costs. That’s why a DTI that looks acceptable to a lender can still feel tight in real life.
The details that trip people up
For credit cards, the lender uses the minimum payment on your statement, not what you actually pay. Carrying a $6,000 balance you plan to pay off next month still adds a minimum payment to your ratio today.
For student loans in deferment or on an income-driven plan, mortgage programs have specific rules for what payment to use, and they don’t always use the payment you actually make. Some programs use a percentage of the balance when the reported payment is zero. Ask the loan officer how your loans will be counted before you assume.
On the income side, lenders want income they can document and expect to continue. Recent raises, new side income, irregular bonuses and self-employment earnings often need a two-year history before they count in full.
Front-end and back-end ratios
Mortgage lenders often look at two versions:
- Front-end ratio: housing costs alone divided by gross income. In the example above, $1,900 / $6,500 is about 29.2%.
- Back-end ratio: all monthly debt, including housing, divided by gross income. That’s the 42.6% figure, and it’s the one that usually decides the application.
When people say “DTI” without qualification, they almost always mean the back-end number.
How high is too high
There’s no single federal cutoff anymore. The well-known 43% limit used to be built into the definition of a qualified mortgage, but the CFPB replaced that limit with a price-based test, and lenders now set DTI ceilings through their own policies and the rules of whoever buys or insures the loan. A few common reference points:
- Conventional loans sold to Fannie Mae: Fannie Mae’s Selling Guide sets a 36% maximum for manually underwritten loans, which can stretch to 45% with stronger credit scores and cash reserves, and up to 50% for loans run through its automated underwriting system.
- FHA loans: HUD’s baseline guidance is commonly summarized as 31% front-end and 43% back-end, with higher ratios allowed when the borrower has compensating factors like significant cash reserves or minimal increase over current rent.
- Auto and personal loans: lenders set their own limits and rarely publish them. Many weigh DTI alongside credit score rather than using a hard cap.
Hitting the maximum isn’t the goal. A lender approving you at 49% means the loan fits their risk model, not that the payment fits your life. Many borrowers aim to keep total DTI in the mid-30s or below so there’s room for savings, repairs and the costs a lender doesn’t count.
Why lenders weigh it so heavily
Credit scores are built on past behavior. DTI measures current capacity. A borrower with spotless history who takes on a payment that eats half their gross pay has very little cushion if hours get cut or a car breaks down. Lenders have seen that pattern lead to defaults, so for larger loans they treat DTI as a gate: if it’s over the line, a strong score usually won’t override it.
It also explains why the amount you’re approved for changes when you add a new car loan between preapproval and closing. The new payment raises your DTI, and the lender reruns the numbers before funding.
Lowering your DTI
There are only two levers: reduce monthly payments or increase documented income. Some moves work faster than others.
- Pay off small installment loans entirely. Eliminating a loan with a few payments left removes that whole payment from the ratio. In the example above, paying off the $450 car loan would bring the DTI from 42.6% to about 35.7%.
- Pay down credit card balances. Lower balances mean lower minimum payments, and the change shows up once the new balance reports to the bureaus. Our guide to credit utilization explains the timing.
- Avoid new debt before applying. No new car, furniture financing or buy-now-pay-later plans while a mortgage application is in progress.
- Rethink the size of the new loan. A smaller loan amount, a larger down payment or a longer term all reduce the payment that goes into the ratio. On a mortgage, the term choice matters a lot; see our comparison of 15- and 30-year mortgages.
- Document all qualifying income. If you have consistent overtime, part-time work or rental income, ask the lender what documentation lets it count.
- Be careful with consolidation. Rolling several debts into one loan with a lower total payment can lower your DTI, but stretching the term can raise what you pay overall. Run both numbers.
- Add a co-borrower with care. A co-borrower’s income counts, but so do their debts, and they become fully responsible for the loan.
If you’re planning a mortgage application in the next six to twelve months, calculate your DTI now using the lender’s rules, not your take-home pay. That gives you time to pay off a small loan or two and walk into the application with numbers that fit.
