House Affordability Calculator

How Much House Can I Afford?

This calculator works backward from your debt-to-income limit: it finds the maximum monthly payment your income and existing debts allow, subtracts your own estimate of property tax, insurance, and PMI/HOA (matching how a lender actually qualifies a full PITI payment), then figures out the largest loan the remaining principal-and-interest budget would support at your entered rate and term, and adds your down payment to get an estimated max home price.

$$\text{Max Principal+Interest Payment} = (\text{Income} \times \text{DTI\%}) - \text{Existing Debts} - \text{Est. Tax+Insurance}$$

The resulting principal-and-interest budget is then converted into a loan amount using the standard amortization formula, solved in reverse for principal instead of payment, and the down payment is added on top of that principal to reach the max home price shown above.

Worked Example

On a 7,000-dollar gross monthly income with 400 dollars in other monthly debts, a 300-dollar estimated monthly property tax and insurance, and a 36% max DTI, the max total debt payment is 2,520 dollars. Subtracting the 400-dollar debts and the 300-dollar tax/insurance estimate leaves 1,820 dollars available for principal and interest. At a 6.5% rate over 30 years, that payment supports a loan of roughly 288,000 dollars. Adding a 40,000-dollar down payment puts the estimated max home price at around 328,000 dollars.

What This Estimate Leaves Out

This calculator factors in your own estimate of monthly property tax, insurance, and PMI/HOA (the field above) when solving for your max loan — matching how lenders actually qualify a full PITI payment against your DTI ratio, not principal and interest alone. What's still simplified: it trusts your entered estimate rather than looking up the real tax rate and insurance cost for a specific home and location, which a real lender will verify and could come out higher or lower than what you entered. Use the Mortgage Calculator once you have a specific home price in mind to see a full payment breakdown with taxes, insurance, and PMI shown as separate escrow lines.

A Brief History of Affordability Standards

Rule-of-thumb guidelines for how much home a borrower can safely afford are a relatively recent, largely regulatory development. Before the 1930s, US home lending had few standardized underwriting rules at all — loan terms and how much a bank was willing to lend varied lender by lender, with no common ratio anchoring the decision. The creation of the Federal Housing Administration in 1934, part of the same National Housing Act that established the modern long-term amortizing mortgage (see the Mortgage Calculator's own history section for that side of the story), also brought standardized underwriting guidelines, including early versions of the income-to-payment ratios still used to judge affordability today.

The specific debt-to-income thresholds in common use now — commonly around 28% of gross income for housing costs alone, and around 36% to 43% for total debt including the mortgage — evolved gradually through decades of FHA, Fannie Mae, and Freddie Mac underwriting guidelines, particularly after the mortgage market's post-2008 overhaul introduced stricter, more standardized "ability to repay" requirements across nearly all US lenders. These ratios are guidelines rather than laws, and individual lenders retain some flexibility to qualify a borrower above or below them depending on credit score, cash reserves, and loan program.

Common Affordability Mistakes

Using take-home (net) pay instead of gross income overstates how much debt you can safely carry, since the standard DTI formula is always based on gross income. Ignoring closing costs — typically 2% to 5% of the home price, on top of the down payment — is another common gap that catches buyers off guard right before closing.

Affordability Terms You Should Know

Debt-to-Income Ratio (DTI) — total monthly debt payments divided by gross monthly income, the main limit this calculator works within.

Principal — the loan amount itself, not counting interest.

PMI (Private Mortgage Insurance) — an added monthly cost required by most lenders when the down payment is below 20% of the home price, not included in this estimate.

This calculator provides estimates for educational and planning purposes only, not lending advice. Actual loan approval depends on credit score, employment history, cash reserves, and a lender's specific underwriting guidelines. Consult a qualified lender for guidance specific to your situation.