Mortgage Affordability Calculator
Use this calculator to estimate the maximum mortgage amount you can afford based on your income, debts, and desired monthly payment.
.calculator-container {
font-family: sans-serif;
border: 1px solid #ccc;
padding: 20px;
border-radius: 8px;
max-width: 500px;
margin: 20px auto;
background-color: #f9f9f9;
}
.calculator-container h2 {
text-align: center;
color: #333;
margin-bottom: 15px;
}
.calculator-container p {
text-align: center;
color: #555;
margin-bottom: 25px;
font-size: 0.95em;
}
.input-section {
display: grid;
grid-template-columns: 1fr;
gap: 15px;
margin-bottom: 20px;
}
.input-section label {
font-weight: bold;
color: #444;
margin-bottom: 5px;
display: block;
}
.input-section input {
width: 100%;
padding: 10px;
border: 1px solid #ddd;
border-radius: 4px;
box-sizing: border-box;
font-size: 1em;
}
button {
background-color: #007bff;
color: white;
padding: 12px 20px;
border: none;
border-radius: 5px;
cursor: pointer;
font-size: 1.1em;
width: 100%;
transition: background-color 0.3s ease;
}
button:hover {
background-color: #0056b3;
}
.result-section {
margin-top: 25px;
padding: 15px;
background-color: #e9ecef;
border: 1px solid #ced4da;
border-radius: 5px;
text-align: center;
font-size: 1.1em;
color: #333;
}
.result-section strong {
color: #28a745;
}
function calculateMortgageAffordability() {
var annualIncome = parseFloat(document.getElementById("annualIncome").value);
var monthlyDebt = parseFloat(document.getElementById("monthlyDebt").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var loanTerm = parseFloat(document.getElementById("loanTerm").value);
var maxPaymentPercentage = parseFloat(document.getElementById("maxPaymentPercentage").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
if (isNaN(annualIncome) || isNaN(monthlyDebt) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTerm) || isNaN(maxPaymentPercentage)) {
resultDiv.innerHTML = "Please enter valid numbers for all fields.";
return;
}
if (annualIncome <= 0 || monthlyDebt < 0 || downPayment < 0 || interestRate <= 0 || loanTerm <= 0 || maxPaymentPercentage 100) {
resultDiv.innerHTML = "Please enter valid positive values. Maximum payment percentage must be between 1 and 100.";
return;
}
var monthlyIncome = annualIncome / 12;
var maxAllowedMonthlyPayment = monthlyIncome * (maxPaymentPercentage / 100);
var maxMonthlyMortgagePayment = maxAllowedMonthlyPayment – monthlyDebt;
if (maxMonthlyMortgagePayment <= 0) {
resultDiv.innerHTML = "Based on your inputs, your debt payments exceed your maximum allowed mortgage payment.
Maximum Affordable Mortgage Loan: $0";
return;
}
var r = (interestRate / 100) / 12; // Monthly interest rate
var n = loanTerm * 12; // Total number of payments
// Mortgage Payment Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
// We need to solve for P (Principal/Loan Amount)
// P = M [ (1 + i)^n – 1] / [ i(1 + i)^n ]
var maxMortgageLoan = maxMonthlyMortgagePayment * (Math.pow(1 + r, n) – 1) / (r * Math.pow(1 + r, n));
// Adjust for down payment to find total home price affordability
var affordableHomePrice = maxMortgageLoan + downPayment;
if (isNaN(maxMortgageLoan) || maxMortgageLoan < 0) {
resultDiv.innerHTML = "Could not calculate mortgage loan amount. Please check your inputs.";
return;
}
resultDiv.innerHTML = "Estimated maximum mortgage loan amount you can afford:
$" + maxMortgageLoan.toFixed(2) + "" +
"Considering your down payment, the estimated affordable home price is:
$" + affordableHomePrice.toFixed(2) + "";
}