Updated · Methodology: named formula library
Mortgage Affordability Calculator
Find out how much house you can afford based on your income, debts, and down payment.
Your estimated monthly mortgage payment is $1,871 for a $300,000 loan at 6.4% over 30 years.
Why This Calculation Matters
The Mortgage Affordability Calculator helps you make better mortgages decisions by putting the math directly in front of you. Instead of relying on averages or guesswork, plug in your own numbers and see how the key inputs, rate, term, amount, and timing, interact. Small changes to any one of them can have outsized effects over years or decades.
How to Use This Calculator
- Enter your values in the input fields, each one has a label and help text explaining what to type.
- Results appear instantly as you type; there's no "calculate" button to press.
- Change any input to compare scenarios side by side.
All math happens in your browser. Nothing you type is sent to a server, saved, or shared.
Key Inputs to Get Right
The most important numbers are usually the interest rate and the time horizon. Over years or decades, small rate differences compound into large dollar differences, so it's worth sanity-checking the rate against current market data before acting on any result.
How Much House Can You Afford?
Lenders typically use the 28/36 rule: your mortgage payment shouldn't exceed 28% of gross monthly income, and total debts shouldn't exceed 36%.
Factors That Affect Affordability
- Income: Higher income means higher affordable payment
- Debts: Existing debts reduce borrowing capacity
- Down payment: Larger down payments mean smaller loans
- Interest rate: Lower rates increase purchasing power
- Property taxes: Vary significantly by location
Worked Example
$300k loan at 7% over 30 years
- principal
- 300000
- rate
- 7
- years
- 30
- Result
- $1,995.91/month
Monthly principal + interest. Total paid: $718,526.69.
When to Use This Calculator
- Model scenarios before making a major financial decision involving mortgages.
- Compare different inputs side by side to see how rate, term, or amount changes your outcome.
- Sanity-check numbers a lender, advisor, or spreadsheet has given you.
- Build a realistic financial plan grounded in your actual numbers, not averages.
Limitations & Common Mistakes
- Results are estimates, actual terms depend on credit, lender policy, taxes, and fees not captured here.
- Rates and prices change daily; recompute with current numbers before signing documents.
- Does not constitute financial advice. For major decisions, consult a licensed advisor.
Frequently Asked Questions
How does the Mortgage Affordability Calculator work?
Enter your loan amount (default: 300000) and any other inputs; the calculator instantly applies its mortgage affordability formula and shows the result with details. All math runs in your browser; nothing is sent to a server.
Is the Mortgage Affordability Calculator accurate for mortgages decisions?
It uses standard, documented formulas that match published references. For high-stakes mortgages decisions, verify the result against an authoritative source (industry calculator, professional advisor, or government data). The calculator is a planning estimate, not a substitute for professional judgment.
What inputs does the Mortgage Affordability Calculator require?
3 inputs: Loan Amount, Interest Rate, Loan Term (years). Each has a sensible default; replace with your own values to get a result tailored to your situation.
Can I bookmark or share the Mortgage Affordability Calculator?
Yes — the URL is stable: https://www.calcintel.com/calculator/mortgage-affordability. Inputs reset to defaults on each visit (no input is stored), so screenshot or copy the result if you want to preserve a specific scenario.
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Key terms
- Debt-to-Income Ratio (DTI)The percentage of your gross monthly income that goes to minimum debt payments. Mortgage underwriters use DTI as the primary affordability gate: most convention…
- Private Mortgage Insurance (PMI)Insurance required by most lenders when a conventional mortgage borrower puts less than 20% down. PMI protects the lender, not the borrower, against default los…
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- Why the 28/36 Rule Fails Most Homebuyers in 2025The classic mortgage-affordability rule was built for a world without student loans, rising property taxes, or $8,000 HOA dues. Here is a better framework, and the DTI math lenders actually use.
Source: BLS Consumer Price Index, 2026.