Debt-to-Income: How Much Can You Borrow?
Before a lender weighs your credit score or your down payment, it asks one blunt question: can you afford this payment on top of what you already owe? The answer is your debt-to-income ratio (DTI), and it quietly sets the ceiling on how much house you can buy.
Two ratios, one that binds
Lenders look at two. The front-end ratio is your housing payment divided by your gross monthly income. The back-end ratio adds all your monthly debts — the new housing payment plus minimum payments on cards, cars, and student loans — over that same income. The back-end is usually the one that binds, because it captures everything you're already committed to.
The 28/36 guideline
The classic rule of thumb is 28/36: keep housing at or under 28% of gross income and total debt at or under 36%. Treat it as a guideline, not a wall — modern automated underwriting (AUS) routinely stretches the back-end into the mid-to-high 40s when the rest of the file is strong: healthy reserves, a high score, or a big down payment. The weaker the file, the closer to 36% they hold you.
| $8,000/mo gross income | Monthly cap |
|---|---|
| 28% housing (front-end) | $2,240 |
| 36% all debt (back-end) | $2,880 |
| …less $700 in car + card payments | $2,180 left for housing |
Here the back-end binds: existing debt pulls the housing budget below the 28% figure. Pay off that $700 and the full $2,240 opens back up.
What counts — and what doesn't
DTI counts your future PITI (principal, interest, taxes, insurance) plus the minimum monthly payments that show on your credit report. It does not count utilities, groceries, insurance premiums, or taxes withheld — real expenses, but not part of the ratio. And it's measured against gross (pre-tax) income, which is why the number can feel more generous than your take-home budget really is.
How to move it
Three levers: lower your monthly debts (retire a small loan, avoid new financing before closing), raise qualifying income, or put more down so the housing payment itself shrinks. Our affordability calculator does the 28/36 math for you, and a bigger down payment is often the fastest way to pull the ratio back under the line.
Common questions
What is a good debt-to-income ratio for a mortgage?
The classic guideline is 28/36 — housing at or under 28% of gross income, total debt at or under 36% — but automated underwriting routinely allows a back-end ratio into the mid-to-high 40s when the rest of the file is strong.
What's the difference between front-end and back-end DTI?
Front-end is just your housing payment divided by gross monthly income. Back-end adds all your monthly debts — cards, cars, student loans — over that same income, and it's usually the ratio that binds.
What counts toward my DTI?
Your future PITI plus the minimum payments that appear on your credit report. Utilities, groceries, insurance premiums and withheld taxes don't count, and it's measured against gross, pre-tax income.
What's the fastest way to lower my DTI?
Retire a small installment loan (a near-finished car note), avoid new financing before closing, or put more down so the housing payment shrinks. Paying off one small loan often frees more borrowing power than months of saving.
By L.W. Martin, Founder — 20 years in the mortgage business, including 15 running his own brokerage. About → · Updated September 2026.