Home Affordability Calculator
The home affordability calculator uses the 28% front-end debt-to-income ratio to estimate the maximum home price a lender is likely to approve. It factors in your monthly debt obligations and down payment to show both the maximum loan amount and the estimated monthly payment.
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Formula
Max Home = Max Loan + Down Payment; Max Loan = MonthlyBudget × [(1+r)^n − 1] / [r × (1+r)^n]
Monthly housing budget equals 28% of gross monthly income. Subtracting existing monthly debt payments gives the maximum mortgage payment. That payment is then used as the annuity payment in the present value of annuity formula to find the maximum loan amount. Adding the down payment yields the maximum home price. r is the monthly interest rate (annual ÷ 12) and n is the total number of payments.
How to use the Home Affordability Calculator
- 1
Enter your annual gross income
Value should be in $.
- 2
Enter your monthly debt payments
Value should be in $.
- 3
Enter your down payment
Value should be in $.
- 4
Enter your mortgage interest rate
Value should be in %.
- 5
Enter your loan term
Value should be in years.
- 6
Read your results instantly
Results update in real time as you type.
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The 28/36 rule explained
Mortgage lenders use debt-to-income (DTI) ratios to assess affordability. The front-end ratio — the 28% rule — says your monthly housing costs (principal, interest, taxes, and insurance) should not exceed 28% of your gross monthly income. The back-end ratio — the 36% rule — says total debt payments including housing should not exceed 36% of gross income.
This calculator uses the 28% front-end ratio as the primary constraint. If you have significant monthly debt payments (car loans, student loans, credit cards), your effective borrowing capacity is reduced because those payments eat into your 28% housing budget.
Note that lenders may approve loans with DTI ratios up to 43% or even higher with compensating factors (large down payment, excellent credit, significant reserves). The 28% threshold is a conservative, widely recommended guideline — not a hard legal limit.
What the 20% down payment really means
A 20% down payment is the conventional threshold that eliminates the requirement for private mortgage insurance (PMI). With less than 20% down, lenders typically require PMI, which adds 0.5-1.5% of the loan amount annually to your costs — on a $300,000 loan, that's $1,500-$4,500 per year.
However, requiring 20% down is increasingly challenging in high-cost markets. FHA loans allow 3.5% down with a 580+ credit score. Conventional loans with PMI start at 3% down. VA loans (for eligible veterans) and USDA loans (for rural properties) require no down payment at all.
The trade-off: a smaller down payment means a larger loan, higher monthly payments, potentially PMI, and more interest over the life of the loan — but it lets you buy sooner and keep more cash liquid for emergencies, improvements, and other investments.
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Hidden costs of homeownership
The calculator shows the mortgage payment, but homeownership comes with additional costs that renters don't face. Property taxes typically run 0.5-2.5% of the home's assessed value annually — on a $350,000 home, that's $1,750-$8,750 per year, or $145-$729 per month. Homeowners insurance averages $1,000-$2,500 annually depending on location and home value.
Maintenance and repairs are the most unpredictable costs. A widely cited guideline is budgeting 1% of the home's value per year for maintenance — $3,500/year on a $350,000 home. Older homes, roofs near the end of life, and aging HVAC systems can push this significantly higher. HOA fees, where applicable, add $200-$600 or more per month.
A practical affordability calculation should add these costs to the mortgage payment to get your true monthly housing cost, then compare that to the 28% guideline. In many markets, total carrying costs on a median home substantially exceed 28% of median household income — which is exactly why housing affordability is a persistent challenge.
Tips & Insights
Pay down debts before applying
Because monthly debt payments directly reduce your maximum mortgage payment (and therefore your loan size), eliminating a $400/month car payment before applying for a mortgage can increase your affordable loan amount by $60,000-$80,000 at current rates. Accelerating payoff of high-payment debts in the 6-12 months before home shopping meaningfully expands your options.
Get pre-approved before house hunting
A pre-approval letter from a lender tells sellers you're serious and gives you a concrete price ceiling. Pre-approval involves a hard credit check and verification of income, assets, and employment. It's different from pre-qualification (which is just an estimate). In competitive markets, sellers often won't consider offers without a pre-approval letter.
Budget for the first-year costs
Closing costs typically run 2-5% of the loan amount — on a $350,000 home, that's $7,000-$17,500 in addition to the down payment. Moving costs, immediate repairs or updates, new furniture, and utility deposits add further. Ensure your financial plan accounts for $10,000-$20,000 in one-time costs beyond the down payment before you close.
Worked Examples
Dual-income household with student loans
A household earning $140,000/year with $800 in monthly debt payments and $60,000 down can afford a home up to approximately $496,000, with a maximum loan of about $436,000 and a monthly mortgage payment of $2,460.
First-time buyer in a moderate-cost market
Earning $75,000/year with $300 monthly debts and $25,000 down, the maximum affordable home price is approximately $228,000, with a loan up to about $203,000 and an estimated monthly payment of $1,450.
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Frequently Asked Questions
How much house can I afford on my salary?
A common starting point is 3-5 times your annual gross income, but this varies significantly based on your down payment, existing debts, local property taxes, and interest rates. The 28% front-end DTI rule is more precise: multiply your gross monthly income by 0.28, subtract existing monthly debt payments, and the result is your maximum monthly mortgage payment. Use that figure in an amortization calculation to find your maximum loan amount.
What credit score do I need to buy a house?
Conventional loans typically require a 620+ credit score, with the best rates reserved for scores above 740. FHA loans allow scores as low as 500 (with 10% down) or 580 (with 3.5% down). VA and USDA loans don't have official minimums, but most lenders require 620+. A higher credit score directly lowers your interest rate, which can mean thousands of dollars in savings over the loan term.
What is PMI and how do I avoid it?
Private mortgage insurance (PMI) protects the lender if you default, and is typically required when your down payment is less than 20%. It costs 0.5-1.5% of the loan amount annually. You can avoid PMI by putting 20% down, using a VA or USDA loan (no PMI required), or using a piggyback loan (80-10-10 structure). You can request PMI cancellation once you reach 20% equity in your home.
Should I buy now or wait for lower rates?
Timing the market is nearly impossible. Higher rates reduce purchasing power, but waiting for lower rates means continued rent payments, missed equity building, and no guarantee rates will fall. A better approach is to buy what you can comfortably afford at current rates. If rates drop significantly, you can refinance. The best time to buy is when you're financially ready — solid down payment, emergency fund intact, and stable income.
How do property taxes and insurance affect affordability?
Property taxes and homeowners insurance are typically included in the 28% housing-cost ratio used by lenders. These costs vary enormously by location — New Jersey and Illinois have property tax rates above 2%, while Hawaii and Alabama are under 0.5%. Before calculating affordability for a specific area, research the local property tax rate and add it to your estimated monthly payment to ensure you stay within your budget.
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