How Much House Can I Afford? Guide to the 28/36 Rule

Buying a home is one of the biggest financial decisions of your life, but banks do not care about your emotions — they calculate strictly by the numbers. Before you fall in love with a property, you need to know exactly what a lender will approve. This guide breaks down the key rules, real math examples, and the hidden costs most buyers overlook.

What Is the 28/36 Rule and How Do Lenders Use It?

Most lenders worldwide determine how much they will lend you using the Debt-to-Income (DTI) ratio. In the US, the classic rule of thumb is the 28/36 rule:

• 28% Front-End Ratio: Your total monthly housing costs — principal, interest, property taxes, and home insurance (often called PITI) — should not exceed 28% of your gross monthly income.
• 36% Back-End Ratio: Your total monthly debt obligations — mortgage plus car loans, credit cards, student loans, and all other debts — should not exceed 36% of your gross monthly income.
• Fannie Mae limits: Under manual underwriting, Fannie Mae's total DTI limit is 36%, rising to 45% with compensating factors. Under its Desktop Underwriter system, the limit can reach 50% with adequate compensating factors.

A Practical Example with Real Numbers

Suppose your gross monthly income is $6,000:

• 28% front-end limit: $6,000 × 0.28 = $1,680 maximum monthly mortgage payment
• 36% back-end limit: $6,000 × 0.36 = $2,160 maximum total monthly debts
• If you already pay $400/month on a car loan, your mortgage ceiling drops to: $2,160 − $400 = $1,760

In this case, the front-end ratio ($1,680) is the binding constraint, so the bank uses the lower figure. The takeaway: every existing debt you carry directly reduces your home-buying power.

Key insight: Under the 28/36 rule, the more restrictive of your two DTI ratios sets your limit. Paying off debts before applying for a mortgage is one of the most effective strategies to increase the loan you qualify for.

How Does the Mortgage Stress Test Work in 2026?

Even if advertised mortgage rates sit at 7.40%, some lenders do not base your approval on today's rate alone. In a stress test, they ask: can you still afford payments if rates rise by 2 percentage points?

Here is how that plays out:

• Advertised rate: 7.40%
• Stress test rate: 9.40%
• Your monthly payment is calculated at 9.40%, not 7.40%
• This significantly reduces the maximum loan amount the bank will approve

Why do stress tests exist? In 2008, millions of homeowners held adjustable-rate mortgages. When rates climbed, monthly payments became unaffordable and foreclosures spiked. Stress tests protect both borrowers and the broader financial system from that scenario repeating.

Which countries use stress tests?

• Canada: A federally mandated test — you must qualify at a stress-test rate set by federal rules, not only at your contract rate
• United Kingdom: Lenders apply individual affordability stress assessments as standard practice
• Australia: Banks typically stress test at a buffer above the loan rate
• United States: FHA, Fannie Mae, and Freddie Mac each have their own qualification ratios and underwriting standards

How Much Home Can You Afford by Income?

The following estimates assume a 30-year mortgage at 7.40% interest (Freddie Mac, October 2026), a 20% down payment, and no significant existing debts:

• $30,000/year income: Max monthly payment ~$700 → Approx. home price $126,000
• $50,000/year income: Max monthly payment ~$1,167 → Approx. home price $211,000
• $80,000/year income: Max monthly payment ~$1,867 → Approx. home price $337,000
• $120,000/year income: Max monthly payment ~$2,800 → Approx. home price $506,000
• $150,000/year income: Max monthly payment ~$3,500 → Approx. home price $632,000

These are approximations. Actual loan amounts depend on your credit score, down payment size, local property taxes, insurance costs, and each lender's specific criteria. Use our calculator for a precise figure.

What Counts as "Housing Costs" in the 28% Calculation?

Many first-time buyers make the mistake of only thinking about the principal and interest payment. Lenders include all of the following in the front-end ratio:

• P — Principal: The portion reducing your outstanding loan balance each month
• I — Interest: The lender's fee for borrowing the money
• T — Taxes: Monthly property tax escrow (varies widely — from 0.3% to 2.5%+ of home value per year depending on location)
• I — Insurance: Homeowner's insurance premium
• PMI: Private Mortgage Insurance if your down payment is below 20% (typically 0.5%–1.5% of the loan per year)
• HOA fees: Monthly homeowners association dues if the property is in a managed community

Worked example: A $300,000 home with 20% down ($240,000 loan) at 7.40% for 30 years:

• Monthly principal + interest: ~$1,662
• Monthly property taxes (estimated): ~$250
• Monthly homeowner's insurance: ~$120
• Total PITI: ~$2,032/month

To comfortably afford this, you need a gross monthly income of at least: $2,032 ÷ 0.28 = $7,257/month (≈$87,000/year)

How Your Credit Score Affects Your Buying Power

Your credit score does not just determine approval — it determines your interest rate, which directly shapes how much home you can afford.

• 760 and above: Best available rates, typically 0.5%–1.0% below the market average
• 700–759: Good rates with a modest premium
• 640–699: Moderate rates with a noticeable premium — can reduce buying power by $20,000–$40,000
• Below 640: Subprime rates or outright denial. In the US, FHA loans need a 580 score for 3.5% down; scores of 500–579 need 10% down, and below 500 is not eligible

The math is stark: On a $300,000 loan over 30 years:

• At 7.40% → monthly payment of $2,077
• At 8.90% (1.5 points higher, for illustration) → monthly payment of $2,392
• Difference: $315/month, or over $113,000 across the life of the loan

Spending a few months improving your credit score before applying for a mortgage is one of the highest-return financial actions you can take.

The Hidden Costs Most Buyers Forget to Budget

Even when you qualify for a loan, you need substantial savings beyond your down payment.

Down Payment Requirements by Country

• US: Conventional loans often require 20% to avoid PMI. FHA loans allow 3.5% down with a credit score of 580 or higher
• Spain/France: Banks finance only part of the appraised value, so expect a substantial down payment
• Germany: A substantial down payment, plus closing costs from personal savings, as banks rarely cover ancillary expenses

Closing Costs by Region

• United States: 2%–5% of the purchase price (appraisal, origination fees, title insurance, escrow)
• United Kingdom: 1%–3% plus Stamp Duty Land Tax (rates vary by purchase price and buyer status)
• Spain: ITP transfer tax, notary, property registry and agency fees
• France: Notary fees, transfer taxes and registration
• Germany: Property transfer tax (Grunderwerbsteuer), notary and broker commission

Post-Purchase Emergency Reserve

Most financial advisors recommend keeping 3–6 months of mortgage payments in liquid savings after closing. Unexpected repairs, an appliance replacement, or a temporary income disruption can otherwise quickly lead to financial stress.

Rule-of-Thumb Home Price Estimates

Several quick estimates are commonly used to ballpark affordability:

• 2.5× to 3× your gross annual income is the traditional upper limit for home prices
• 4× to 5× annual income is more realistic in high-cost cities like London, Sydney, or San Francisco
• No more than 30% of your net take-home pay on total housing costs is a popular budgeting guideline

However, rules of thumb are a starting point, not a substitute for the real calculation. The only reliable path to knowing your actual buying power is to:

1. Calculate your DTI with all current debts included
2. Look up today's prevailing mortgage rates in your area
3. Factor in local property taxes, insurance, and any HOA dues
4. Get a formal mortgage pre-approval from a lender

Should You Borrow the Maximum the Bank Will Approve?

Just because a bank offers you a $500,000 mortgage does not mean you should take it. Becoming "house poor" — spending so much on housing that savings, investments, and quality of life suffer — is a real and common outcome of borrowing at the maximum limit.

Consider borrowing below your ceiling if:

• You have variable or seasonal income (freelancers, self-employed, commission earners)
• You plan to start a family or take parental leave within the loan term
• You have not yet built a 6-month emergency fund
• You have other significant financial goals (retirement savings, business investment, debt repayment)

A financially sustainable mortgage is one you could still make payments on if your income dropped by 15%–20%.

Key Takeaways

• The 28/36 rule is the classic rule of thumb for mortgage affordability, while lenders apply their own limits, such as Fannie Mae's 36%–50% DTI caps
• Stress tests, where they apply, make you qualify at a rate above what you will actually pay — plan accordingly
• Your credit score, existing debts, down payment, and local taxes each directly shape how much home you can realistically afford
• Budget for closing costs (typically 2%–5% of the purchase price in the US) and keep an emergency fund after closing
• Borrow what is comfortable, not the maximum the bank will approve — the two numbers are rarely the same

Use our free affordability calculator to get a personalized estimate based on your exact income, current debts, and target property value.

Calculate My Affordability Now

Sources

• Freddie Mac, Primary Mortgage Market Survey: https://www.freddiemac.com/pmms
• Fannie Mae Selling Guide B3-6-02, Debt-to-Income Ratios: https://selling-guide.fanniemae.com/sel/b3-6-02/debt-income-ratios
• HUD Mortgagee Letter 2010-29, Minimum Credit Scores and Loan-to-Value Ratios: https://www.hud.gov/sites/documents/10-29ml.pdf