"How much house can I afford?" is the first real question every buyer asks, and the answer is rarely the number a lender flashes on a pre-approval letter. A bank tells you the maximum it's willing to risk. The smarter question is how much house keeps your budget comfortable when property taxes jump, the water heater dies, and your income takes an unexpected hit. The classic framework for answering that is the 28/36 rule, and once you understand it you'll never look at a listing price the same way again.
What the 28/36 Rule Actually Means
The 28/36 rule is a pair of guardrails that mortgage lenders and financial planners use to keep your housing payment in line with your income. It breaks down into two ratios, both based on your gross monthly income (your pay before taxes and deductions):
- The 28% front-end ratio: No more than 28% of your gross monthly income should go to housing costs. That "housing" number isn't just the loan payment, it's PITI: Principal, Interest, property Taxes, and homeowners Insurance, plus any HOA dues and PMI.
- The 36% back-end ratio: No more than 36% of your gross monthly income should go to all recurring debt combined, housing plus car loans, student loans, credit card minimums, and personal loans.
Think of the front-end number as your housing ceiling and the back-end number as your total-debt ceiling. You have to pass both tests. If your other debts are heavy, the 36% rule will cap your house even when the 28% rule says you could spend more. That's the rule working exactly as intended, it's protecting you from being "house poor."
The Formula: How to Run Your Own Numbers
The math is refreshingly simple. Start with your gross monthly income, then multiply:
- Max housing payment = Gross monthly income × 0.28
- Max total debt = Gross monthly income × 0.36
- Max housing payment (debt-adjusted) = (Gross monthly income × 0.36) − existing monthly debt payments
Your true housing budget is the lower of the first and third lines. Our Home Affordability Calculator automates all of this in seconds, and the Debt-to-Income Calculator shows exactly where you stand on the back-end ratio before you ever talk to a lender.
A Fully Worked Example at $90,000 Income
Let's run a realistic 2025 scenario. Meet Jordan, who earns $90,000 a year, which is $7,500 in gross monthly income. Jordan has a $400 monthly car payment and $250 in student loans, for $650 of existing monthly debt.
| Step | Calculation | Result |
|---|---|---|
| Gross monthly income | $90,000 ÷ 12 | $7,500 |
| 28% front-end (max housing) | $7,500 × 0.28 | $2,100/mo |
| 36% back-end (max total debt) | $7,500 × 0.36 | $2,700/mo |
| Existing debt to subtract | $400 car + $250 student | $650/mo |
| Housing allowed under back-end rule | $2,700 − $650 | $2,050/mo |
| True housing budget (lower of the two) | min($2,100, $2,050) | $2,050/mo |
Jordan's housing ceiling is $2,050 per month, set by the back-end ratio because of that existing debt. Now we have to translate that PITI budget into a home price. Remember, the $2,050 has to cover taxes and insurance too, not just principal and interest. A reasonable split sets aside roughly $350/month for property taxes, insurance, and PMI, leaving about $1,700 for principal and interest.
At a 6.8% 30-year fixed rate (a typical 2025 figure), $1,700/month of principal and interest supports a loan of roughly $260,000. Add a 10% down payment (about $29,000) and Jordan can comfortably target a home priced near $289,000. Our Down Payment Calculator helps you test how different down payments shift that final price.
How Income, Debt, Down Payment, and Rate Change Everything
The 28/36 rule isn't static, every input moves the needle. Here's how each lever works:
- Income: The most direct lever. If Jordan earned $110,000 ($9,167/month), the front-end budget jumps to about $2,567 and the back-end budget to $3,300, dramatically expanding the price range.
- Existing debt: Every $100 of monthly debt you carry shaves $100 off your back-end housing budget. Paying off that $400 car loan would have lifted Jordan's housing ceiling from $2,050 back up to the full $2,100, and freed cash flow on top of it.
- Down payment: A bigger down payment lowers the loan amount and your monthly payment, and crossing the 20% threshold eliminates PMI entirely. That's often $100 to $250/month back in your pocket.
- Interest rate: This is the quiet giant. On a $260,000 loan, moving from 6.8% to 7.8% raises the monthly principal and interest by roughly $175, which can push you back over your 28% ceiling and force a cheaper house. A single percentage point can cut your buying power by tens of thousands of dollars.
The Hidden Costs Buyers Forget
The biggest mistake first-time buyers make is comparing a rent payment to a mortgage's principal and interest, while ignoring everything else homeownership piles on. Budget for all of it:
- Property taxes: Vary wildly by state, from under 0.4% of home value annually in Hawaii to over 2% in New Jersey and Illinois. On a $289,000 home that can range from roughly $1,150 to $5,800 per year.
- Homeowners insurance: Nationally averaging around $1,900 to $2,400 per year in 2025, and far higher in storm- or wildfire-prone regions.
- PMI (Private Mortgage Insurance): Required on most conventional loans with less than 20% down, typically 0.3% to 1.5% of the loan amount per year. On a $260,000 loan that's roughly $65 to $325 a month.
- Maintenance and repairs: A widely used rule of thumb is 1% of the home's value per year, so about $2,900 annually on a $289,000 home. Roofs, HVAC systems, and appliances don't last forever.
- HOA dues: Condos and planned communities can charge anywhere from $200 to $700+ per month, and lenders count this against your front-end ratio.
- Closing costs: Typically 2% to 5% of the loan, due upfront, separate from your down payment.
These costs are exactly why the 28% rule bundles taxes and insurance into the housing number instead of looking at principal and interest alone. Leave them out and you'll "afford" a house that quietly drowns you.
Lenders Will Approve More, Here's Why You Should Be Careful
If you apply for a mortgage, you'll likely discover that lenders will approve a back-end DTI well above 36%. Qualified Mortgage rules and programs make room for higher ratios: many conventional loans backed by Fannie Mae and Freddie Mac allow DTIs up to 45%, and sometimes 50% with strong compensating factors, while FHA loans can stretch to 43% to 50%+.
Just because you can borrow at a 45% DTI doesn't mean you should. At those levels, nearly half your gross income is committed to debt before you've paid for food, gas, childcare, retirement savings, or a single emergency. A higher DTI also means less cushion if rates on variable debt rise or your income dips. The 28/36 rule is intentionally conservative because it leaves breathing room, and breathing room is what keeps a home a blessing instead of a trap.
A reasonable middle path: use the 28/36 rule as your target, treat the high-30s as a stretch you enter with eyes open, and avoid the 43%+ territory unless you have substantial savings and rock-solid job security. Run your real numbers through the Debt-to-Income Calculator first so there are no surprises.
How the Rule Shifts Across Income Levels
To see how powerfully income drives affordability, here's the same 28/36 math applied across several 2025 salaries, assuming $650 of existing monthly debt and the same 6.8% rate, 10% down, and roughly $350/month for taxes and insurance. The numbers show why even a modest raise meaningfully expands what you can buy:
| Annual income | Gross monthly | 28% housing cap | Budget after debt | Approx. home price |
|---|---|---|---|---|
| $60,000 | $5,000 | $1,400 | $1,150 | ~$136,000 |
| $90,000 | $7,500 | $2,100 | $2,050 | ~$289,000 |
| $120,000 | $10,000 | $2,800 | $2,800 | ~$418,000 |
| $150,000 | $12,500 | $3,500 | $3,500 | ~$537,000 |
Notice that at $60,000 and $90,000 the back-end rule still binds because of the existing debt, but by $120,000 the front-end 28% cap takes over since the fixed $650 of debt is a smaller share of a larger income. These are illustrative estimates, your local taxes, insurance, and rate will shift the final price, which is exactly why running your own figures through the Home Affordability Calculator beats relying on a generic chart.
Common Mistakes to Avoid
- Using net income instead of gross. The 28/36 rule is always based on pre-tax income. Using your take-home pay will understate your budget and confuse the math.
- Forgetting taxes and insurance. Your real housing payment is PITI, not just the loan. Always include escrow.
- Maxing out the pre-approval. The lender's max is a ceiling, not a recommendation. Build in room for life.
- Ignoring future debt. Planning to finance a car or take on student loans soon? Factor that into your back-end ratio today.
- Draining savings for the down payment. Closing costs, moving expenses, and an emergency fund all need cash too. Don't show up to closing with an empty account.
Putting It All Together
The 28/36 rule gives you a fast, reliable answer to "how much house can I afford?" Cap housing at 28% of gross monthly income, cap total debt at 36%, and remember that the lower of those two ceilings is your real budget. Then layer in the hidden costs, taxes, insurance, PMI, maintenance, and HOA, that turn a listing price into a true monthly obligation. Lenders may bless a bigger number, but the borrower who buys a little under their max is the one who sleeps well at night. Plug your figures into our Home Affordability Calculator, Debt-to-Income Calculator, and Down Payment Calculator to see your personal numbers, then go house hunting with a budget you actually believe in.
This article is for general educational purposes only and is not financial, lending, or tax advice. Rates, taxes, insurance costs, and loan-program limits change frequently and vary by location and lender. Confirm your specific numbers with a licensed mortgage professional before making a decision.
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