This calculator helps you estimate how much you can afford to borrow for a mortgage. It takes into account your income, existing debts, and desired loan term.
#mortgage-calculator-container {
font-family: Arial, sans-serif;
max-width: 600px;
margin: 20px auto;
padding: 20px;
border: 1px solid #ccc;
border-radius: 8px;
box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}
#mortgage-calculator-container h2 {
text-align: center;
margin-bottom: 20px;
color: #333;
}
#mortgage-calculator-container p {
text-align: justify;
margin-bottom: 20px;
color: #555;
line-height: 1.5;
}
.calculator-inputs {
display: grid;
grid-template-columns: repeat(auto-fit, minmax(250px, 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 #ddd;
border-radius: 4px;
box-sizing: border-box;
width: 100%;
}
button {
display: block;
width: 100%;
padding: 12px;
background-color: #007bff;
color: white;
border: none;
border-radius: 4px;
font-size: 16px;
cursor: pointer;
transition: background-color 0.3s ease;
}
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: 1.1em;
color: #333;
min-height: 50px; /* To prevent layout shifts */
}
function calculateMortgageAffordability() {
var grossAnnualIncome = parseFloat(document.getElementById("grossAnnualIncome").value);
var monthlyDebtPayments = parseFloat(document.getElementById("monthlyDebtPayments").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var loanTermYears = parseFloat(document.getElementById("loanTermYears").value);
var propertyTaxesAnnual = parseFloat(document.getElementById("propertyTaxesAnnual").value);
var homeownersInsuranceAnnual = parseFloat(document.getElementById("homeownersInsuranceAnnual").value);
var privateMortgageInsurance = parseFloat(document.getElementById("privateMortgageInsurance").value);
var resultDiv = document.getElementById("result");
if (isNaN(grossAnnualIncome) || isNaN(monthlyDebtPayments) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTermYears) || isNaN(propertyTaxesAnnual) || isNaN(homeownersInsuranceAnnual) || isNaN(privateMortgageInsurance)) {
resultDiv.innerHTML = "Please enter valid numbers for all fields.";
return;
}
// Lender's debt-to-income (DTI) ratio rules of thumb.
// Generally, lenders look at two ratios:
// 1. Front-end ratio (housing expenses / gross income) – often capped around 28%
// 2. Back-end ratio (total debt payments / gross income) – often capped around 36%
// We'll use a conservative back-end DTI of 40% for affordability calculation.
var maxDTI = 0.40; // 40% debt-to-income ratio
var maxMonthlyObligations = (grossAnnualIncome / 12) * maxDTI;
var availableForMortgage = maxMonthlyObligations – monthlyDebtPayments;
if (availableForMortgage 0 && numberOfPayments > 0) {
monthlyPaymentFactor = (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments)) / (Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1);
}
var propertyTaxesMonthly = propertyTaxesAnnual / 12;
var homeownersInsuranceMonthly = homeownersInsuranceAnnual / 12;
var totalMonthlyHousingCosts = availableForMortgage;
var totalMonthlyNonPAndI = propertyTaxesMonthly + homeownersInsuranceMonthly + privateMortgageInsurance;
var maxMonthlyPI = totalMonthlyHousingCosts – totalMonthlyNonPAndI;
if (maxMonthlyPI 0) {
maxLoanAmount = maxMonthlyPI / monthlyPaymentFactor;
}
var maxPurchasePrice = maxLoanAmount + downPayment;
resultDiv.innerHTML = "Estimated Maximum Mortgage Loan Amount: $" + maxLoanAmount.toFixed(2) + "" +
"Estimated Maximum Purchase Price: $" + maxPurchasePrice.toFixed(2) + "" +
"Based on a max DTI of 40%, and estimated monthly taxes, insurance, and PMI.";
}