Mortgage rates get all the headlines, but there's a quieter number that can kill your home loan application before a lender ever mentions the interest rate.
It's your debt-to-income ratio, or DTI, and it's one of the biggest reasons buyers get turned down in 2025.
Add up every monthly debt payment — car loans, student loans, minimum credit card payments, personal loans.
Divide that by your gross monthly income.
That percentage is your DTI, and lenders treat it like a report card on whether you can actually afford a house.
The magic number most conventional lenders watch is 36%.
Cross it, and you're in what the industry politely calls a "higher-risk" bucket.
Go above 43% on a qualified mortgage, and many lenders won't approve you at all — though FHA loans and some programs stretch closer to 50% with compensating factors like cash reserves or a bigger down payment.
Because lenders got burned in 2008 and regulators tightened the screws.
The Consumer Financial Protection Bureau's qualified mortgage rules effectively made 43% a ceiling for loans that meet certain legal protections.
That's not a law banning higher DTIs, but in practice it shapes what banks will write.
What counts against you might surprise you.
Student loans get counted even if you're on an income-driven repayment plan — sometimes at 1% of the balance rather than your actual payment.
A $60,000 student loan balance can add $500 to your monthly debt figure on paper, even if you're paying $150.
Lenders also count child support, co-signed loans you're not actually paying, and that timeshare maintenance fee you forgot about.
Pay down revolving debt first — credit cards hurt your DTI dollar-for-dollar and carry the highest interest.
Avoid financing a car in the six months before you apply for a mortgage.
Don't close old credit cards, since that can shrink your available credit and spike your utilization.
And if you're close to the line, a larger down payment or a lender that manually underwrites your file can make the difference.
There's also a workaround buyers overlook: adding a co-borrower with strong income and low debt can pull your combined DTI into range.
It's not romantic, but neither is renting for another two years.
One more thing worth questioning: the 43% rule isn't really about whether *you* can afford the payment.
It's about whether the lender can sell your loan on the secondary market.
Fannie Mae and Freddie Mac have DTI limits baked into their underwriting systems, and lenders rarely fight them.
So the number protecting you and the number protecting the bank's pipeline aren't always the same thing.
If you're shopping right now, run your own DTI before a loan officer does.
It takes ten minutes with a calculator and a recent pay stub, and it tells you whether you're wasting weekends touring houses you can't finance.
Our take: DTI is a blunt instrument that punishes people with student loans and childcare costs while rewarding those who simply carry less debt on paper.
Final Thoughts
It's worth knowing the rules cold, because the system won't explain them to you — and the people who benefit most from you not understanding them are the ones selling the loan.