This calculator helps you estimate the maximum mortgage loan you might be able to afford based on your income, debts, and desired down payment. Remember, this is an estimate, and lenders will consider many other factors.
function calculateMortgageAffordability() {
var annualIncome = parseFloat(document.getElementById("annualIncome").value);
var existingDebtPayments = parseFloat(document.getElementById("existingDebtPayments").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var loanTerm = parseFloat(document.getElementById("loanTerm").value);
var propertyTaxRate = parseFloat(document.getElementById("propertyTaxRate").value);
var homeInsurance = parseFloat(document.getElementById("homeInsurance").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
// Input validation
if (isNaN(annualIncome) || annualIncome <= 0 ||
isNaN(existingDebtPayments) || existingDebtPayments < 0 ||
isNaN(downPayment) || downPayment < 0 ||
isNaN(interestRate) || interestRate <= 0 ||
isNaN(loanTerm) || loanTerm <= 0 ||
isNaN(propertyTaxRate) || propertyTaxRate <= 0 ||
isNaN(homeInsurance) || homeInsurance < 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
// Lender typically allows PITI (Principal, Interest, Taxes, Insurance) to be 28-36% of gross monthly income.
// We'll use a common guideline of 36% for affordability calculation.
var maxPITIPercentage = 0.36;
var maxMonthlyHousingPayment = (annualIncome / 12) * maxPITIPercentage;
// Lender also considers Debt-to-Income ratio, usually capped around 43-50%.
// Let's assume the housing payment (PITI) is part of this overall DTI.
// We can simplify this by saying the total monthly debt + PITI shouldn't exceed a certain percentage of gross monthly income.
// For simplicity in this calculator, we'll focus on the housing payment limit and subtract existing debts.
var availableForMortgagePrincipalAndInterest = maxMonthlyHousingPayment – existingDebtPayments – (homeInsurance / 12) – ((annualIncome / 12) * (propertyTaxRate / 100));
if (availableForMortgagePrincipalAndInterest 0) {
var numerator = Math.pow(1 + monthlyInterestRate, numberOfMonths) – 1;
var denominator = monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfMonths);
principalAmount = availableForMortgagePrincipalAndInterest * (numerator / denominator);
} else { // Handle 0% interest rate (unlikely for mortgages, but for completeness)
principalAmount = availableForMortgagePrincipalAndInterest * numberOfMonths;
}
var estimatedMaxHomePrice = principalAmount + downPayment;
// Format results
var formattedPrincipal = principalAmount.toLocaleString(undefined, { style: 'currency', currency: 'USD' });
var formattedMaxHomePrice = estimatedMaxHomePrice.toLocaleString(undefined, { style: 'currency', currency: 'USD' });
var formattedMonthlyPayment = availableForMortgagePrincipalAndInterest.toLocaleString(undefined, { style: 'currency', currency: 'USD' });
resultDiv.innerHTML =
"Estimated Maximum Loan Amount You Can Afford: " + formattedPrincipal + "" +
"Estimated Maximum Home Price You Can Afford (including down payment): " + formattedMaxHomePrice + "" +
"Note: This is a rough estimate. Your actual affordability will depend on lender underwriting, credit score, loan type, and other factors. The estimated monthly payment for Principal, Interest, Taxes, and Insurance (PITI) used in this calculation is approximately " + formattedMonthlyPayment + " per month.";
}
.calculator-container {
font-family: sans-serif;
border: 1px solid #ccc;
padding: 20px;
border-radius: 8px;
max-width: 600px;
margin: 20px auto;
background-color: #f9f9f9;
}
.calculator-container h2 {
text-align: center;
color: #333;
margin-bottom: 15px;
}
.calculator-container p {
font-size: 0.95em;
line-height: 1.5;
color: #555;
margin-bottom: 15px;
}
.input-section {
margin-bottom: 15px;
}
.input-section label {
display: block;
margin-bottom: 5px;
font-weight: bold;
color: #444;
}
.input-section input[type="number"] {
width: calc(100% – 12px);
padding: 8px;
border: 1px solid #ddd;
border-radius: 4px;
font-size: 1em;
}
.calculator-container button {
display: block;
width: 100%;
padding: 10px 15px;
background-color: #007bff;
color: white;
border: none;
border-radius: 4px;
font-size: 1.1em;
cursor: pointer;
transition: background-color 0.3s ease;
}
.calculator-container button:hover {
background-color: #0056b3;
}
#result {
margin-top: 20px;
padding: 15px;
background-color: #e9ecef;
border: 1px solid #ced4da;
border-radius: 4px;
text-align: center;
font-size: 1.05em;
}
#result p {
margin-bottom: 8px;
}
#result em {
font-size: 0.85em;
color: #6c757d;
}