Mortgage Affordability Calculator: How Much House Can You Actually Afford?

The bank says you can afford a $450,000 house. Your mortgage broker agrees. The online calculator at every major real estate site confirms it. They are all wrong — or more precisely, they are all answering a different question than the one you should be asking.

The question the bank answers is: “What is the maximum loan we can approve based on your income, debts, and credit score?” The question you should answer is: “What monthly housing cost can I sustain comfortably while still saving, investing, and living the life I want?” These two numbers are almost never the same, and the gap between them is where financial stress lives.

Banks approve mortgages using a debt-to-income (DTI) ratio, typically capping total monthly debt payments at 43–50% of gross income. A household earning $120,000 annually ($10,000/month gross) with $500 in existing debt payments could qualify for a mortgage payment of roughly $3,800–$4,500/month. At 6.37% on a 30-year loan, that translates to a home price of $500,000–$600,000.

That number ignores property taxes, homeowners insurance (which has risen 46% since 2021), maintenance (the 1% Rule suggests budgeting 1% of the home’s value annually), HOA fees, utility costs that may differ from your current situation, and the fact that DTI ratios are calculated on gross income — not the take-home pay that actually funds your life.

This spreadsheet calculates what you can actually afford by modelling total monthly housing cost — not just the mortgage payment.

Disclaimer: This calculator is provided for informational and educational purposes only. It does not constitute financial or mortgage advice. Consult a qualified mortgage professional before making home purchase decisions. SpreadsheetTemplates.info is not responsible for decisions made based on the information provided.

Why the Bank’s Number Is Too High#

The editorial position is clear: for most households, borrowing the maximum amount a bank will approve is a path to being “house poor” — a situation where the mortgage is technically affordable on paper but leaves no margin for saving, investing, unexpected expenses, or the lifestyle choices that make life worth living.

The DTI Problem#

Banks use gross income for DTI calculations, but nobody lives on gross income. After federal taxes, state taxes, FICA, retirement contributions, and health insurance premiums, take-home pay is typically 60–75% of gross income. A mortgage payment that represents 28% of gross income might represent 38–45% of net income. That is a very different number and a very different experience.

The Hidden Costs Problem#

The mortgage payment (principal + interest) is only one component of housing cost. A realistic total monthly housing cost includes the mortgage payment (P&I), property taxes (varies enormously by jurisdiction — from under 0.5% in Hawaii to over 2% in New Jersey and Illinois), homeowners insurance (average $3,057/year nationally in 2026, but dramatically higher in climate-affected states), private mortgage insurance (PMI, if your down payment is less than 20% — typically 0.5–1.5% of the loan amount annually), HOA or condo fees (if applicable — can range from $100 to $1,000+/month), maintenance and repairs (the 1% Rule: budget 1% of the home’s value per year, or about $4,000 annually on a $400,000 home), and utilities (which may increase significantly if moving from a smaller space).

On a $400,000 home with a 6.37% mortgage, 20% down, $5,000/year in property taxes, and $3,000/year in insurance, the total monthly housing cost is approximately $3,100 — of which only $2,000 is the mortgage payment. The remaining $1,100 in taxes, insurance, and maintenance is invisible in the bank’s approval but very visible in your bank account.

The Opportunity Cost Problem#

Every dollar committed to housing is a dollar not available for retirement savings, investment, emergency reserves, education funding, travel, or other priorities. A household that stretches to the bank’s maximum mortgage may technically make every payment but sacrifice wealth-building opportunities that compound over decades.

The rule of thumb: your total monthly housing cost (including all the components above) should not exceed 25–30% of your take-home pay. The bank’s DTI calculation may approve you for 40%+. The 25–30% target leaves room for everything else.

What the Spreadsheet Calculates#

Inputs#

You enter your household gross annual income, monthly take-home pay (after taxes, retirement contributions, and insurance deductions), existing monthly debt payments (car loans, student loans, credit cards — everything except the proposed mortgage), the home purchase price, your planned down payment amount or percentage, the expected interest rate (currently around 6.37% for 30-year fixed, approximately 5.7% for 15-year fixed as of April 2026), and the loan term (the tool compares 15-year and 30-year options automatically).

You also enter property-specific costs: estimated annual property taxes, estimated annual homeowners insurance, any HOA or condo fees, and PMI rate (if applicable).

Outputs#

The spreadsheet produces a complete monthly cost breakdown showing the mortgage payment (P&I), property taxes, homeowners insurance, PMI (if applicable), HOA fees, maintenance reserve (1% of home value, divided by 12), and total monthly housing cost.

It then calculates three affordability ratios: total housing cost as a percentage of gross income (the bank’s view), total housing cost as a percentage of net income (the realistic view), and total housing cost plus existing debt as a percentage of net income (the complete financial picture).

A 15-year vs 30-year comparison shows the trade-off: the 15-year option has a higher monthly payment but produces dramatically lower total interest over the life of the loan. The spreadsheet shows both the monthly payment difference and the total interest savings.

Finally, a “maximum comfortable price” calculation works backward from your net income, applying the 25–30% housing cost target to determine the highest price you can afford while maintaining financial flexibility.

How to Use the Spreadsheet#

Step 1: Start with your income and debts. Enter gross and net income and all existing debt payments. Be honest and thorough — missed debts produce inaccurate results.

Step 2: Enter the property details. If you have a specific property in mind, enter its price and the property-specific costs. If you are in the exploration phase, enter a target price and estimated costs for the area where you are looking. Property tax rates are available from your county assessor’s office; insurance estimates can be gathered using our home insurance comparison spreadsheet.

Step 3: Review the affordability ratios. The “net income” ratio is the one that matters most. If total housing cost exceeds 30% of your take-home pay, you are stretching. If it exceeds 35%, you are likely to feel constrained. If it exceeds 40%, reconsider the purchase price.

Step 4: Compare 15-year vs 30-year. If the 15-year payment fits within your 25–30% net income target, it is almost always the better choice. You build equity faster, pay dramatically less interest, and own the home outright in half the time. At current rates, the difference in total interest between a 15-year and 30-year mortgage on a $320,000 loan is well over $100,000.

Step 5: Run the “maximum comfortable price” calculation. This is the most useful output for the exploration phase. It tells you the highest home price that keeps your total housing cost within the 25–30% net income range, given your specific income, debts, and local cost assumptions.

Download: Mortgage Affordability Calculator — Excel (.xlsx)

The 2026 Rate Environment and Affordability#

Current mortgage rates are reshaping what affordability means for buyers.

At 6.37% for a 30-year fixed (as of April 2026), the monthly payment on a $320,000 loan (corresponding to a $400,000 home with 20% down) is approximately $2,000. At the 2021 pandemic-era low of 2.65%, the same loan would have cost $1,290/month. That is a $710/month difference — $8,520/year — solely from interest rates.

The forecasts offer some optimism. Morgan Stanley projects rates could reach 5.50–5.75% by mid-2026, while the MBA expects rates near 6.30% through the year. Fannie Mae sees rates dipping just under 6% by year-end. Even a 0.5% rate reduction from current levels would save approximately $100/month on a $320,000 loan.

For buyers weighing whether to purchase now or wait for lower rates: the affordability calculator helps you model both scenarios. Enter today’s rate and see the monthly cost. Then enter a hypothetical lower rate and see how it changes. The trade-off is clear: waiting for lower rates risks higher home prices (which Morgan Stanley projects to rise 2% in 2026), while buying now at a higher rate can be refinanced later if rates drop. Our mortgage refinance calculator models that refinance scenario precisely.

Beyond the Calculator: Additional Affordability Factors#

Several factors fall outside the spreadsheet but should inform your decision.

Job stability and income trajectory. A mortgage is a 15–30 year commitment. If your income is variable, seasonal, or at risk of disruption, borrowing conservatively is even more important. If your income is likely to grow significantly over the next 3–5 years, today’s stretch may become tomorrow’s comfort — but do not bet on income growth that has not materialised.

Dual-income dependency. If your affordability calculation requires both incomes, consider what happens if one income is temporarily or permanently lost. Maternity or paternity leave, job loss, illness, or a decision to change careers can all affect a two-income household. A mortgage that is comfortable on two incomes but unmanageable on one is a risk worth understanding.

Competing financial goals. If you are also saving for retirement, building an emergency fund, paying off student loans, or planning for children’s education, the housing budget competes with all of these. The spreadsheet’s net-income-based affordability ratio helps, but only you can decide how to allocate among competing priorities.

Location-specific costs. Property taxes vary from under 0.5% (Hawaii, Alabama) to over 2% (New Jersey, Illinois, Texas). On a $400,000 home, that is the difference between $2,000 and $8,000+ per year. Insurance costs are equally variable — $1,500/year in some markets, $5,000+ in Florida and climate-affected states. These location-specific costs can shift your affordability by tens of thousands of dollars over the life of the mortgage.

For a broader view of all the tools available for real estate analysis, see our complete guide to real estate investment spreadsheet tools.

Frequently Asked Questions#

What percentage of my income should go to housing?

Target 25–30% of your take-home (net) pay for total housing costs, including mortgage, taxes, insurance, maintenance, and HOA. This is more conservative than the bank’s DTI ratio (which uses gross income and allows 28–36%) but leaves meaningful room for saving, investing, and unexpected expenses.

Should I put 20% down or use a smaller down payment?

Putting 20% down eliminates PMI ($100–$300+/month on a typical loan) and gives you immediate equity cushion. However, if it depletes your savings entirely, a 10–15% down payment with PMI may be the wiser choice — you maintain a financial buffer and can request PMI removal once you reach 20% equity through payments and appreciation. The spreadsheet models both scenarios.

Is a 15-year mortgage better than a 30-year?

Financially, the 15-year mortgage is almost always superior: you pay dramatically less total interest and build equity faster. The trade-off is a higher monthly payment (typically 30–40% more than the 30-year). If the 15-year payment fits within the 25–30% net income target, it is the better choice. If it pushes you above that threshold, the 30-year provides necessary flexibility — and you can always make extra principal payments voluntarily.

How much should I budget for maintenance?

The 1% Rule (1% of home value per year) is the standard guideline. On a $400,000 home, that is $4,000/year or $333/month. Newer homes in good condition may cost less; older homes or properties with deferred maintenance may cost more. This is an average — some years you spend nothing, other years a roof or HVAC replacement creates a large expense. Budget for the average.

Should I buy now or wait for lower rates?

Nobody can predict rates with certainty. If you find a home that meets your needs at a price within your comfortable affordability range at current rates, buying is defensible. You can refinance later if rates drop. Waiting risks higher home prices, increased competition when rates do drop (more buyers re-enter the market), and the opportunity cost of continued renting. The decision should be based on your personal financial readiness, not on rate speculation.

How do I account for property taxes if I don’t know the exact amount?

Look up the property tax rate for the county or municipality where you are buying (available from the county assessor’s website) and multiply by the purchase price. Be aware that some jurisdictions reassess the property at the sale price, which may be higher than the previous owner’s assessed value. Budget for the reassessed amount, not the seller’s current tax bill.

Can I use this calculator if I’m self-employed?

Yes, but the income inputs require more care. Use your net self-employment income (after business expenses and self-employment taxes) as your gross income figure. Your take-home pay should reflect actual cash available after all business and personal expenses. Lenders typically require two years of self-employment tax returns for mortgage qualification, and they use the lower of the two years — so your qualification amount may be less than your current income suggests.

What is PMI and how do I avoid it?

Private Mortgage Insurance protects the lender (not you) if you default with less than 20% equity. It typically costs 0.5–1.5% of the loan amount annually, added to your monthly payment. You avoid it by making a 20% or larger down payment. You can also request PMI removal once your loan-to-value ratio reaches 80% through a combination of payments and appreciation (you may need an appraisal to confirm the value). The spreadsheet models PMI cost so you can see the impact of different down payment scenarios.