Mortgage lenders have quietly tightened the math on who qualifies for a home loan, and the number doing most of the gatekeeping isn't your credit score.
It's your debt-to-income ratio, or DTI — a simple division problem that compares what you owe each month to what you earn.
Get it wrong, and you can be looking at a mortgage payment hundreds of dollars higher, or no approval at all.
Add up every monthly debt payment: car loan, student loans, minimum credit card payments, personal loans, plus the estimated new mortgage payment.
Divide that total by your gross monthly income before taxes.
If you bring home $7,000 a month and your debts total $2,800, your DTI is 40%.
The magic thresholds matter more than most buyers realize.
Conventional loans sold to Fannie Mae and Freddie Mac generally cap DTI at 45% to 50%, with 43% acting as a practical comfort line.
FHA loans typically allow up to 43%, stretchable to around 50% with compensating factors.
Cross 50%, and most lenders stop the conversation entirely regardless of how much cash you have saved.
Higher rates mean the same house now eats a bigger slice of your paycheck.
A $350,000 loan at 6.5% runs about $2,212 a month in principal and interest.
At 3% — the rate many buyers locked in three years ago — that same loan cost $1,475.
The debt side of the equation did, and it's pushing thousands of otherwise qualified buyers over the limit.
Lenders charge higher rates to borrowers with DTIs above roughly 43%, often adding 0.25% to 0.75% to your interest.
On a $350,000 loan, half a percentage point costs about $110 extra per month — roughly $40,000 over a 30-year term.
If you're close to the line, three moves work faster than saving more.
Paying down revolving credit card balances lowers your minimum payments and moves the ratio immediately, sometimes within one billing cycle.
Refinancing a car loan to a shorter term can cut the monthly figure even if the total cost is similar.
And adding a co-borrower with steady income raises the denominator, which is often the quickest fix available.
One caution: don't open new credit, co-sign a loan for a family member, or finance furniture in the months before applying.
Each of those shows up as a new monthly obligation, and underwriters recheck your file right before closing.
Start by pulling your actual minimum payments from your statements rather than guessing, then run the division.
Knowing your number before a lender does gives you time to fix it — and time is the one input you can control.
The bottom line: DTI has become the quiet arbiter of who gets to buy a home in this market, and most buyers don't learn their number until it's too late to change it.
Final Thoughts
Treat it like a credit score — check it early, watch it monthly, and never let it drift past 43% if you can help it.