Mortgage Affordability Calculator
Understanding how much house you can afford is a crucial first step in the home-buying process. This mortgage affordability calculator helps you estimate your potential borrowing power based on your income, debts, and desired down payment. It considers key factors like your gross monthly income, existing monthly debt payments, and the estimated interest rate on the mortgage. Remember, this is an estimate, and your actual borrowing capacity will be determined by lenders based on a comprehensive review of your financial situation.
function calculateAffordability() {
var grossMonthlyIncome = parseFloat(document.getElementById("grossMonthlyIncome").value);
var monthlyDebtPayments = parseFloat(document.getElementById("monthlyDebtPayments").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var loanTerm = parseFloat(document.getElementById("loanTerm").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
if (isNaN(grossMonthlyIncome) || isNaN(monthlyDebtPayments) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTerm)) {
resultDiv.innerHTML = "Please enter valid numbers for all fields.";
return;
}
// A common guideline is that your total housing payment (principal, interest, taxes, insurance) shouldn't exceed 28% of your gross monthly income.
// Also, your total debt payments (including housing) shouldn't exceed 36% of your gross monthly income. We'll use the more conservative 36% for total debt allowance.
var maxTotalDebtPayment = grossMonthlyIncome * 0.36;
var availableForMortgagePayment = maxTotalDebtPayment – monthlyDebtPayments;
if (availableForMortgagePayment 0) {
maxLoanAmount = availableForMortgagePayment * Math.pow(1 + monthlyInterestRate, loanTermMonths) / (Math.pow(1 + monthlyInterestRate, loanTermMonths) – 1);
} else {
// If interest rate is 0, the calculation is simpler: Principal = Monthly Payment * Number of Months
maxLoanAmount = availableForMortgagePayment * loanTermMonths;
}
// The total affordable home price is the maximum loan amount plus the down payment.
var affordableHomePrice = maxLoanAmount + downPayment;
resultDiv.innerHTML =
"Based on your inputs, your estimated maximum affordable home price is:
$" + affordableHomePrice.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,') + "" +
"Estimated maximum loan amount:
$" + maxLoanAmount.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,') + "" +
"
This is an estimate. Lenders will conduct a full financial assessment. Factors like credit score, property taxes, homeowner's insurance, and PMI (if applicable) will also affect your actual mortgage payment and affordability.";
}
.calculator-container {
font-family: sans-serif;
max-width: 600px;
margin: 20px auto;
padding: 20px;
border: 1px solid #ddd;
border-radius: 8px;
box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}
.calculator-container h2 {
text-align: center;
color: #333;
margin-bottom: 15px;
}
.calculator-container p {
color: #555;
line-height: 1.6;
margin-bottom: 20px;
}
.calculator-inputs {
display: grid;
grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
gap: 15px;
margin-bottom: 20px;
}
.form-group {
display: flex;
flex-direction: column;
}
.form-group label {
margin-bottom: 5px;
font-weight: bold;
color: #444;
}
.form-group input {
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 1em;
}
.calculator-inputs button {
grid-column: 1 / -1; /* Span across all columns */
padding: 12px 20px;
background-color: #007bff;
color: white;
border: none;
border-radius: 4px;
font-size: 1.1em;
cursor: pointer;
transition: background-color 0.3s ease;
}
.calculator-inputs button:hover {
background-color: #0056b3;
}
.calculator-result {
margin-top: 20px;
padding: 15px;
background-color: #e9ecef;
border: 1px solid #dee2e6;
border-radius: 4px;
text-align: center;
}
.calculator-result p {
margin-bottom: 10px;
color: #333;
}
.calculator-result strong {
color: #28a745;
}
.calculator-result em {
font-size: 0.9em;
color: #6c757d;
}