Mortgage Affordability Calculator

Mortgage Affordability Calculator Explained

This mortgage affordability calculator helps answer the classic question: “How much house can I afford?” It uses common U.S. lender guidelines to estimate a comfortable maximum home price based on income, debts, interest rate, and typical housing costs.

How affordability is calculated

Most lenders look at two key ratios, often called the 28/36 rule:

• Front-end ratio (28%) – maximum share of income that should go to housing only (mortgage, taxes, insurance, HOA).
• Back-end ratio (36%) – maximum share of income that should go to housing plus all other monthly debts.

The calculator:

1. Converts your annual income to gross monthly income.
2. Calculates the maximum housing payment allowed by the 28% rule.
3. Calculates the maximum housing payment allowed when total debts stay under 36%.
4. Chooses the lower of the two as your allowed housing payment.
5. Uses your interest rate, loan term, taxes, insurance and HOA to back into an estimated maximum home price.

What this calculator takes into account

The estimate includes:

• Principal and interest (mortgage payment)
• Property taxes (as % of home value per year)
• Homeowners insurance (as % of home value per year)
• HOA fees (flat amount per month)
• Existing monthly debts (car loans, student loans, credit cards, etc.)
• Down payment amount

This gives a more realistic monthly payment than just principal and interest alone.

Example affordability scenario

• Annual income: $90,000
• Other monthly debts: $600
• Down payment: $40,000
• Interest rate: 6.5%
• Loan term: 30 years
• Property tax: 1.2% of home value per year
• Homeowners insurance: 0.4% per year
• HOA fees: $150/month

With typical 28/36 ratios, the calculator might estimate:

• Maximum monthly housing payment: around 28% of income minus other debts.
• Maximum home price in the mid-$300,000s to low-$400,000s range (depending on exact assumptions).

These numbers are only an estimate, but they provide a realistic starting point before talking to lenders.

Why income alone is not enough

Two people with the same income can afford very different homes, because:

• One may have no debt, the other may have car loans and student loans.
• Property tax and insurance rates vary by location.
• HOA fees can add hundreds of dollars to the monthly payment.

That is why this calculator uses both income and debt when estimating affordability.

Front-end vs back-end ratio

• Front-end ratio = housing payment ÷ gross monthly income.
• Back-end ratio = (housing payment + other debts) ÷ gross monthly income.

Typical target ranges in the U.S.:

• Front-end: ≤ 28%
• Back-end: ≤ 36% (sometimes up to 43% for certain programs)

The calculator uses the stricter of the two limits when estimating your allowed housing payment.

How down payment changes affordability

A larger down payment:

• Lowers the loan amount
• Reduces the monthly principal and interest payment
• Can help avoid PMI if you reach 20% equity

Use the calculator to test different down payment amounts and see how much additional home price they unlock.

FAQ

Is this a mortgage pre-approval?
No. This calculator provides an estimate for educational purposes. Only a lender can provide an official pre-approval based on credit score, documentation and full underwriting.

Can I go above the suggested amount?
Some lenders may allow higher debt-to-income ratios, but this increases financial risk. The 28/36 guideline is designed to keep payments comfortable.

Does this include closing costs?
This calculator focuses on monthly affordability and home price, not cash needed at closing. You will typically need extra funds for closing costs on top of your down payment.

What if my debts are high?
High existing monthly debts can reduce the home price you can safely afford. Paying down debt before taking on a mortgage can significantly improve your affordability.

Use this mortgage affordability calculator as a starting point to understand your price range before you start shopping for homes or talking to real estate agents.