Please enter valid positive numbers for Income and Interest Rate.
Maximum Home Price:–
Loan Amount:–
Max Monthly Payment (P&I + Escrow):–
Debt-to-Income (DTI) Limit Used:–
How Much House Can You Really Afford?
Determining your budget is the critical first step in the home buying process. This House Affordability Calculator goes beyond simple multiplication. It uses the standard lender qualification ratios (DTI) to estimate a realistic purchase price based on your income, existing debts, and specific property costs like taxes and insurance.
Understanding the 28/36 Rule
Lenders typically use two main ratios to decide how much they will lend to you. Our calculator checks both and uses the conservative limit:
Front-End Ratio (28%): Historically, lenders prefer that your housing costs (Principal, Interest, Taxes, Insurance, and HOA) do not exceed 28% of your gross monthly income.
Back-End Ratio (36%): This ratio looks at your total debt load. It implies that your housing costs plus all other monthly debts (credit cards, student loans, car payments) should not exceed 36% of your gross monthly income. Note: FHA and some conventional loans may allow higher ratios (up to 43% or 50%), but 36% is a safe baseline for financial health.
Key Factors That Impact Buying Power
Even with a high income, several variables can drastically reduce the price of the home you can afford:
1. Interest Rates
The interest rate is the most volatile factor. A 1% increase in interest rates can reduce your buying power by roughly 10%. When rates are high, your monthly payment covers less principal, meaning you can borrow less money for the same monthly cost.
2. Monthly Debts
High student loan payments or car leases directly reduce the amount available for a mortgage. Eliminating a $500 monthly car payment can potentially increase your home buying budget by $70,000 to $80,000, depending on current rates.
3. Property Taxes and HOA
Not all monthly payments go toward the loan. In high-tax areas or communities with expensive Homeowners Association (HOA) dues, a significant portion of your "payment capacity" is eaten up by these sunk costs, lowering the mortgage amount you qualify for.
How to Use This Calculator
To get the most accurate result, use the gross income found on your W-2s or tax returns (before taxes are taken out). For monthly debts, sum up the minimum monthly payments found on your credit report. Do not include utilities or groceries—only contractual debt obligations.
function calculateAffordability() {
// 1. Get Input Values
var grossIncome = document.getElementById("grossIncome").value;
var monthlyDebts = document.getElementById("monthlyDebts").value;
var downPayment = document.getElementById("downPayment").value;
var interestRate = document.getElementById("interestRate").value;
var loanTerm = document.getElementById("loanTerm").value;
var propertyTax = document.getElementById("propertyTax").value;
var homeInsurance = document.getElementById("homeInsurance").value;
var hoaDues = document.getElementById("hoaDues").value;
// 2. Parse and Validate
var incomeVal = parseFloat(grossIncome);
var debtsVal = parseFloat(monthlyDebts);
var downVal = parseFloat(downPayment);
var rateVal = parseFloat(interestRate);
var termVal = parseFloat(loanTerm);
var taxVal = parseFloat(propertyTax);
var insuranceVal = parseFloat(homeInsurance);
var hoaVal = parseFloat(hoaDues);
var errorDiv = document.getElementById("errorDisplay");
var resultsDiv = document.getElementById("results");
// Simple validation checks
if (isNaN(incomeVal) || incomeVal <= 0 || isNaN(rateVal) || rateVal <= 0 || isNaN(termVal) || termVal <= 0) {
errorDiv.style.display = "block";
resultsDiv.style.display = "none";
return;
}
// Handle empty or NaN optional fields by defaulting to 0
if (isNaN(debtsVal)) debtsVal = 0;
if (isNaN(downVal)) downVal = 0;
if (isNaN(taxVal)) taxVal = 0;
if (isNaN(insuranceVal)) insuranceVal = 0;
if (isNaN(hoaVal)) hoaVal = 0;
errorDiv.style.display = "none";
// 3. Calculation Logic (The 28/36 Rule)
var monthlyIncome = incomeVal / 12;
var monthlyTax = taxVal / 12;
var monthlyInsurance = insuranceVal / 12;
// Front-End Ratio Limit (28% of Income)
// This limit is for PITI + HOA
var limitFrontEnd = monthlyIncome * 0.28;
// Back-End Ratio Limit (36% of Income)
// This limit is for (PITI + HOA) + Other Debts
// So, available for housing = (Income * 0.36) – Other Debts
var limitBackEnd = (monthlyIncome * 0.36) – debtsVal;
// The maximum allowable total monthly housing payment is the LOWER of the two
var maxTotalHousingPayment = Math.min(limitFrontEnd, limitBackEnd);
// Determine which rule limited the budget for display purposes
var limitUsedText = (limitFrontEnd < limitBackEnd) ? "28% Front-End Ratio" : "36% Back-End Ratio";
// If debts are too high, maxTotalHousingPayment might be negative
if (maxTotalHousingPayment <= 0) {
document.getElementById("resHomePrice").innerText = "$0";
document.getElementById("resLoanAmount").innerText = "$0";
document.getElementById("resMonthlyPayment").innerText = "$0";
document.getElementById("resDTIUsed").innerText = "Debt load too high";
resultsDiv.style.display = "block";
return;
}
// Calculate available amount for Principal & Interest (P&I)
// Subtract Taxes, Insurance, and HOA from the max housing payment
var availableForPI = maxTotalHousingPayment – monthlyTax – monthlyInsurance – hoaVal;
if (availableForPI <= 0) {
document.getElementById("resHomePrice").innerText = "$0 (Taxes/HOA exceed limit)";
document.getElementById("resLoanAmount").innerText = "$0";
document.getElementById("resMonthlyPayment").innerText = "$" + maxTotalHousingPayment.toLocaleString(undefined, {minimumFractionDigits: 0, maximumFractionDigits: 0});
document.getElementById("resDTIUsed").innerText = limitUsedText;
resultsDiv.style.display = "block";
return;
}
// Calculate Max Loan Amount based on available P&I
// Formula: P = (r * PV) / (1 – (1 + r)^-n)
// Inverted for PV (Loan Amount): PV = (P * (1 – (1 + r)^-n)) / r
var monthlyRate = rateVal / 100 / 12;
var numberOfPayments = termVal * 12;
// PV = P&I * [ ( (1+r)^n – 1 ) / ( r * (1+r)^n ) ]
var mathPow = Math.pow(1 + monthlyRate, numberOfPayments);
var maxLoanAmount = availableForPI * ( (mathPow – 1) / (monthlyRate * mathPow) );
// Total Home Price = Max Loan + Down Payment
var maxHomePrice = maxLoanAmount + downVal;
// 4. Output Results
document.getElementById("resHomePrice").innerText = "$" + Math.floor(maxHomePrice).toLocaleString();
document.getElementById("resLoanAmount").innerText = "$" + Math.floor(maxLoanAmount).toLocaleString();
document.getElementById("resMonthlyPayment").innerText = "$" + Math.floor(maxTotalHousingPayment).toLocaleString() + "/mo";
document.getElementById("resDTIUsed").innerText = limitUsedText;
resultsDiv.style.display = "block";
}