This calculator helps you estimate how much home you can realistically afford based on your income, debt, and down payment. Understanding your potential mortgage affordability is a crucial first step in the home-buying process. It allows you to set realistic expectations and focus your search on properties within your budget.
How it works: The calculator takes into account your gross monthly income, your existing monthly debt payments, and the percentage of the home price you plan to put down as a down payment. It then estimates the maximum monthly mortgage payment you might qualify for, which can be translated into an estimated home price. Remember, this is an estimation, and actual loan approval will depend on lender-specific criteria, credit score, and current market conditions.
function calculateAffordability() {
var grossMonthlyIncome = parseFloat(document.getElementById("grossMonthlyIncome").value);
var monthlyDebtPayments = parseFloat(document.getElementById("monthlyDebtPayments").value);
var downPaymentPercentage = parseFloat(document.getElementById("downPaymentPercentage").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var loanTermYears = parseFloat(document.getElementById("loanTermYears").value);
var resultElement = document.getElementById("result");
resultElement.innerHTML = ""; // Clear previous results
// — Input Validation —
if (isNaN(grossMonthlyIncome) || grossMonthlyIncome <= 0) {
resultElement.innerHTML = "Please enter a valid Gross Monthly Income.";
return;
}
if (isNaN(monthlyDebtPayments) || monthlyDebtPayments < 0) {
resultElement.innerHTML = "Please enter a valid Total Monthly Debt Payments.";
return;
}
if (isNaN(downPaymentPercentage) || downPaymentPercentage 100) {
resultElement.innerHTML = "Please enter a Down Payment Percentage between 0 and 100.";
return;
}
if (isNaN(interestRate) || interestRate <= 0) {
resultElement.innerHTML = "Please enter a valid Annual Interest Rate.";
return;
}
if (isNaN(loanTermYears) || loanTermYears <= 0) {
resultElement.innerHTML = "Please enter a valid Loan Term in Years.";
return;
}
// — Affordability Calculation Logic —
// General rule of thumb: Debt-to-income ratio (DTI) should not exceed 36%-43% for housing costs.
// We'll use a conservative 36% for principal, interest, taxes, and insurance (PITI).
var maxHousingPaymentRatio = 0.36;
var maxTotalDebtRatio = 0.43; // Including housing and other debts
// Calculate maximum affordable monthly payment based on DTI
var maxAllowedMonthlyPayment = grossMonthlyIncome * maxHousingPaymentRatio;
// Ensure total debt (including estimated housing) doesn't exceed total DTI limit
var maxTotalMonthlyObligations = grossMonthlyIncome * maxTotalDebtRatio;
var maxHousingPaymentConsideringOtherDebts = maxTotalMonthlyObligations – monthlyDebtPayments;
// The actual maximum monthly housing payment is the lower of the two limits
var estimatedMaxMonthlyMortgagePayment = Math.min(maxAllowedMonthlyPayment, maxHousingPaymentConsideringOtherDebts);
if (estimatedMaxMonthlyMortgagePayment 0) {
maxLoanAmount = estimatedMaxMonthlyMortgagePayment * (1 – Math.pow(1 + monthlyInterestRate, -numberOfPayments)) / monthlyInterestRate;
} else {
// Handle zero interest rate case
maxLoanAmount = estimatedMaxMonthlyMortgagePayment * numberOfPayments;
}
// Calculate estimated maximum home price
var downPaymentAmount = maxLoanAmount * (downPaymentPercentage / 100);
var estimatedMaxHomePrice = maxLoanAmount + downPaymentAmount;
// Display Results
resultElement.innerHTML =
"Estimated Maximum Monthly Mortgage Payment (PITI): $" + estimatedMaxMonthlyMortgagePayment.toFixed(2) + "" +
"Estimated Maximum Loan Amount: $" + maxLoanAmount.toFixed(2) + "" +
"Estimated Maximum Home Price: $" + estimatedMaxHomePrice.toFixed(2) + "" +
"Note: This is an estimate. Actual affordability depends on lender, credit score, taxes, insurance, and HOA fees. PITI includes Principal, Interest, Taxes, and Insurance.";
}
.calculator-container {
font-family: sans-serif;
max-width: 700px;
margin: 20px auto;
padding: 20px;
border: 1px solid #ddd;
border-radius: 8px;
background-color: #f9f9f9;
}
.calculator-container h2 {
text-align: center;
color: #333;
margin-bottom: 15px;
}
.calculator-container p {
color: #555;
line-height: 1.6;
margin-bottom: 15px;
}
.calculator-inputs {
display: grid;
grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
gap: 15px;
margin-bottom: 20px;
}
.input-group {
display: flex;
flex-direction: column;
}
.input-group label {
margin-bottom: 5px;
font-weight: bold;
color: #444;
}
.input-group input {
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 1rem;
}
.calculator-container button {
display: block;
width: 100%;
padding: 12px 20px;
background-color: #007bff;
color: white;
border: none;
border-radius: 5px;
font-size: 1.1rem;
cursor: pointer;
transition: background-color 0.3s ease;
}
.calculator-container button:hover {
background-color: #0056b3;
}
.calculator-result {
margin-top: 25px;
padding: 15px;
border: 1px dashed #aaa;
border-radius: 5px;
background-color: #fff;
text-align: center;
}
.calculator-result p {
margin-bottom: 10px;
}