Mortgage rates have cooled from their 2023 peaks, and plenty of buyers are rushing to find out what they can afford.
But there's a gatekeeper that trips up more applicants than any interest rate: your debt-to-income ratio, or DTI.
It's the single number that can sink a loan application even when your credit score looks great.
Add up every monthly debt payment — car loans, student loans, minimum credit card payments, personal loans, plus the new mortgage you're hoping to get.
Divide that total by your gross monthly income.
That percentage is your DTI, and lenders treat it as a snapshot of how much breathing room your budget has left.
The magic number most conventional lenders want to see is 36% or lower.
Go above 43%, and you're in dangerous territory for a qualified mortgage — many lenders simply won't approve you.
Some government-backed loans, like FHA mortgages, allow ratios up to around 50% with compensating factors, but that doesn't mean you should aim there.
A 780 credit score means you pay bills on time, but it says nothing about whether you can absorb a $2,400 housing payment on top of a $600 car note and $300 in card minimums.
Lenders learned that lesson the hard way in 2008, and DTI became the guardrail.
Paying down revolving debt is the fastest fix, since credit cards carry the highest minimum payments relative to their balances.
Knocking $5,000 off a card balance can shave several points off your ratio.
Paying off a small car loan entirely can help too, even if the monthly payment was modest.
Lenders generally count student loan payments even when they're deferred or in income-driven repayment — sometimes using 1% of the balance as the assumed payment.
Co-signed loans count against you too, even if someone else is paying them.
And don't open a new credit card or finance furniture in the months before applying; that inquiry and new minimum payment can quietly push you over the line.
If your DTI is stubbornly high, you have options.
A larger down payment lowers the loan amount and the monthly payment.
Adding a co-borrower with steady income changes the math entirely.
Some buyers use a gift from family for the down payment, which lenders typically allow with a letter.
Others wait six to twelve months and attack debt aggressively.
One more thing worth knowing: Fannie Mae and Freddie Mac generally cap DTI at 50% for the loans they buy, but many lenders set their own stricter limits — often 45% or even 43%.
Two lenders can look at the same file and reach different conclusions, which is why shopping around matters more than ever.
Run your own numbers before you talk to anyone.
Take your gross monthly income, list every minimum payment, and do the division yourself.
Knowing your ratio ahead of time turns a stressful application into a straightforward conversation — and it tells you exactly which debts to kill first.
The takeaway: your DTI isn't just paperwork, it's a budget mirror.
Final Thoughts
If the number feels tight, the house probably will too, no matter what the rate says.