Mortgage lenders have a number in mind before you ever sit down at the closing table, and it has nothing to do with your credit score.
It's called your debt-to-income ratio, or DTI, and it quietly decides whether you get approved, what rate you're offered, and how much house you can actually afford.
Here's the simple version: your DTI is all your monthly debt payments divided by your gross monthly income.
Add up a car loan, student loans, minimum credit card payments, and the projected new mortgage payment.
Divide that by what you earn before taxes.
The result is a percentage that lenders treat like a pass-fail exam.
Most conventional loans follow what's called the 43% rule, though many lenders will stretch to 45% or even 50% for strong borrowers.
Government-backed FHA loans can go higher, sometimes into the mid-50s.
Cross those lines and you'll either get denied or get quoted a higher rate to offset the perceived risk.
The trap is that buyers often calculate affordability using take-home pay.
Lenders use gross income, so the number on your offer letter looks bigger than what actually hits your bank account.
That gap is where budgets quietly fall apart after closing.
A household earning $7,000 a month gross with a $400 car payment, $250 in student loans, and $150 in minimum card payments has $800 in existing debt.
At a 43% cap, that leaves roughly $2,210 for a mortgage payment, including taxes and insurance.
In many metros, that buys a lot less house than buyers expect.
First, paying down revolving balances lowers your minimum payments, which drops your DTI faster than almost anything else.
Second, shopping at least three lenders matters, because DTI limits and rate pricing vary more than most people realize.
Self-employed buyers and anyone with variable income should expect extra scrutiny.
Lenders may average two years of tax returns, and write-offs that lower your tax bill also lower the income they count.
If you're house hunting right now, run your own DTI before a lender does.
It takes ten minutes and can save you from falling in love with a house you can't close on.
Our take: DTI is boring, but it's the single most useful number in the mortgage process.
Final Thoughts
Know yours before you tour a single listing, and you'll negotiate from a position of strength instead of hope.