Mortgage lenders are looking at one number before they ever talk about your credit score, and most homebuyers have no idea what it is.
Get it wrong, and you can have an 800 credit score and still get turned down.
Your DTI is all your monthly debt payments divided by your gross monthly income.
If you bring in $6,000 a month before taxes and owe $1,800 across a car loan, student loans, and minimum credit card payments, your DTI is 30%.
Lenders traditionally want that number at or below 36% once your new mortgage payment is included.
Many conventional loans now allow up to 43%, and some government-backed loans stretch to 50%.
But crossing into the 40s usually means a higher interest rate or a smaller loan than you hoped for.
Your future mortgage payment includes principal, interest, property taxes, homeowners insurance, and HOA dues.
That full number gets added to your existing debts before the math is done.
A $1,600 housing payment can push a comfortable-looking budget over the line fast.
Rent usually isn't included, since lenders assume it goes away when you buy.
Utility bills, phone plans, and streaming subscriptions typically don't count either.
But a cosigned loan for a family member absolutely does, even if you never make a payment on it.
If your ratio is too high, you have a few levers.
Paying down credit cards helps more than most people realize, because it lowers your minimum payments.
Paying off a small car loan entirely can knock several points off your DTI overnight.
Waiting for a raise or a bonus to show up on pay stubs also works, though lenders usually want to see it for a couple of months.
Buying points to lower your rate won't fix DTI, but it can shrink the monthly payment enough to matter.
Putting more money down does the same thing.
And in some cases, adding a co-borrower with steady income can bring the ratio down dramatically, though it ties that person to the loan.
One warning: don't open a new credit card or finance furniture while you're house hunting.
A single new minimum payment can flip an approval into a denial, sometimes days before closing.
Lenders often recheck your credit right before funding.
Before you tour a single house, grab your last two pay stubs and add up every minimum debt payment you make.
If the number lands near 40% or higher, spend a few months fixing it first.
You'll likely qualify for a better rate and a payment you can actually live with.
This is the least glamorous part of buying a home, and it's the part that quietly saves or costs people tens of thousands over a 30-year loan.
Final Thoughts
A little math before the open house beats a rejection letter after it.