Figuring out how much house you can afford is one of the most important financial decisions you'll make. The answer involves more than just your income. It depends on your debts, your down payment, the interest rate you qualify for, and how much ongoing cost you can absorb comfortably. Getting this wrong in either direction, buying too much house or being overly conservative, has real consequences.
The 28/36 Rule
The 28/36 rule is the most widely used starting point for estimating housing affordability.
- 28%: Your total monthly housing costs (mortgage principal and interest, property taxes, homeowner's insurance, and HOA fees if applicable) should not exceed 28% of your gross monthly income.
- 36%: Your total monthly debt payments (housing costs plus all other debts like car loans, student loans, and credit cards) should not exceed 36% of your gross monthly income.
Example: If your gross household income is $8,000/month:
- Max housing payment: $8,000 × 0.28 = $2,240
- Max total debt: $8,000 × 0.36 = $2,880
If you already have $500/month in car and student loan payments, your housing budget under the 36% rule is $2,880 - $500 = $2,380, not the full $2,240 allowed by the 28% rule alone.
These are guidelines, not hard limits. Some loan programs allow higher ratios. But exceeding them typically means less financial cushion for emergencies, maintenance, or income disruptions.
What Lenders Actually Look At
Lenders evaluate your application using several factors, not just income.
Debt-to-Income Ratio (DTI)
DTI is the lender's primary affordability measure. It compares your total monthly debt payments to your gross monthly income. Most conventional loans allow a DTI up to 43-45%. Some programs allow higher with compensating factors (large down payment, strong credit, substantial reserves).
Credit Score
Your credit score affects the interest rate you're offered, which directly impacts your monthly payment and how much house that payment can support. A borrower with a 760 score and a borrower with a 680 score can qualify for the same loan but at meaningfully different rates.
Down Payment
A larger down payment reduces the loan balance, which lowers the monthly payment and improves DTI ratios. It also eliminates private mortgage insurance (PMI) if you put down 20% or more on a conventional loan. PMI typically adds 0.5-1.5% of the loan amount per year to your cost.
Cash Reserves
Many lenders want to see that you have reserves remaining after closing, typically 2-6 months of housing payments in accessible accounts. Reserves signal that you can handle unexpected expenses without defaulting.
Approved vs. Affordable: Not the Same Thing
Lenders will approve you for the maximum they're willing to lend based on their underwriting guidelines. That number is not a budget recommendation.
Just because you qualify for a $500,000 mortgage doesn't mean a $500,000 mortgage is right for your life. Lenders don't know your actual spending priorities, job security, family plans, or risk tolerance. They're evaluating risk on a loan, not planning your finances.
Many financial advisors suggest being more conservative than lender maximums, especially when:
- Your income is variable or commission-based
- You have limited emergency reserves
- You anticipate major expenses (children, aging parents, career changes)
- You're buying in a market where values are uncertain
A useful personal test: if you lost your job tomorrow, how long could you cover your housing costs? If the answer is less than 3-6 months, you may be buying at the edge of your capacity.
Hidden Costs Buyers Frequently Underestimate
The mortgage payment is only part of the cost of owning a home.
Property taxes: These vary dramatically by location. In some areas, taxes add $500-$1,000 or more per month to the cost of ownership on a mid-priced home.
Homeowner's insurance: Required by lenders. Rates vary by location, property type, and coverage level.
HOA fees: In condos, townhouses, and many planned communities, HOA fees can range from $100 to $1,000+ per month. They're non-negotiable and often increase over time.
Maintenance and repairs: A commonly used estimate is 1% of home value per year for upkeep. On a $400,000 home, that's $4,000/year ($333/month) on average. Older homes, or homes with aging systems, tend to cost more.
Closing costs: Typically 2-5% of the loan amount, paid at purchase. This is separate from your down payment.
Buyers who focus only on the mortgage payment are often surprised by the true monthly cost of ownership once all these categories are added up.
Conservative vs. Aggressive Approaches
A conservative buyer targets a housing payment at 20-25% of gross income, leaves a larger down payment to minimize leverage, and keeps total debt well below 36% of income. This approach preserves financial flexibility and resilience.
An aggressive buyer uses the maximum DTI lenders allow, minimizes the down payment to preserve liquidity, and accepts PMI costs in exchange for getting into a higher-priced property sooner. This can work well if income grows steadily and the market appreciates, but it leaves less room for error.
Neither approach is universally right. The best answer depends on your specific income stability, existing savings, local market conditions, and long-term plans.
Use an Affordability Calculator
To model your specific numbers, including income, debts, down payment, interest rate, property taxes, and insurance, use the Mortgage Affordability Calculator. It translates all these inputs into an estimated maximum purchase price and monthly payment, so you can enter the market with a realistic number rather than a guess.