Mortgage Affordability Calculator
Buying a home is a significant financial decision, and understanding how much you can realistically afford is crucial. This mortgage affordability calculator helps you estimate the maximum mortgage loan you might qualify for based on your income, debts, and desired down payment. Remember, this is an estimate, and your actual loan approval will depend on lender-specific criteria, credit score, and a full financial assessment.
.calculator-container {
font-family: sans-serif;
max-width: 600px;
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: 20px;
}
.calculator-form .form-group {
margin-bottom: 15px;
}
.calculator-form label {
display: block;
margin-bottom: 5px;
font-weight: bold;
color: #555;
}
.calculator-form input[type="number"] {
width: calc(100% – 22px);
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
box-sizing: border-box;
}
.calculator-form 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;
}
.calculator-form button:hover {
background-color: #0056b3;
}
.calculator-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;
}
.calculator-result strong {
color: #007bff;
}
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 propertyTaxes = parseFloat(document.getElementById("propertyTaxes").value);
var homeownersInsurance = parseFloat(document.getElementById("homeownersInsurance").value);
var privateMortgageInsurance = parseFloat(document.getElementById("privateMortgageInsurance").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
// — Input Validation —
if (isNaN(grossMonthlyIncome) || grossMonthlyIncome < 0 ||
isNaN(monthlyDebtPayments) || monthlyDebtPayments < 0 ||
isNaN(downPayment) || downPayment < 0 ||
isNaN(interestRate) || interestRate <= 0 ||
isNaN(loanTerm) || loanTerm <= 0 ||
isNaN(propertyTaxes) || propertyTaxes < 0 ||
isNaN(homeownersInsurance) || homeownersInsurance < 0 ||
isNaN(privateMortgageInsurance) || privateMortgageInsurance < 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
// — Constants and Conversions —
var maxDebtToIncomeRatio = 0.43; // Commonly used max DTI ratio for mortgage lenders
var monthlyInterestRate = (interestRate / 100) / 12;
var numberOfMonths = loanTerm * 12;
// — Calculations —
// 1. Calculate maximum monthly housing payment (PITI) allowed based on DTI
var maxHousingPayment = (grossMonthlyIncome * maxDebtToIncomeRatio) – monthlyDebtPayments;
if (maxHousingPayment <= 0) {
resultDiv.innerHTML = "Based on your income and existing debts, it may be difficult to qualify for a mortgage at this time. Consult with a mortgage professional.";
return;
}
// 2. Calculate estimated monthly costs for taxes, insurance, and PMI
var monthlyPropertyTaxes = propertyTaxes / 12;
var monthlyHomeownersInsurance = homeownersInsurance / 12;
var monthlyPMI = privateMortgageInsurance / 12;
var totalMonthlyNonPrincipalInterest = monthlyPropertyTaxes + monthlyHomeownersInsurance + monthlyPMI;
// 3. Calculate maximum affordable monthly principal and interest (P&I) payment
var maxPIPayment = maxHousingPayment – totalMonthlyNonPrincipalInterest;
if (maxPIPayment 0) {
var numerator = Math.pow(1 + monthlyInterestRate, numberOfMonths) – 1;
var denominator = monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfMonths);
maxLoanAmount = maxPIPayment * (numerator / denominator);
} else {
// Handle 0% interest rate case (though highly unlikely for mortgages)
maxLoanAmount = maxPIPayment * numberOfMonths;
}
// 5. Calculate the total estimated home price you can afford
var estimatedHomePrice = maxLoanAmount + downPayment;
// — Display Results —
resultDiv.innerHTML = "Based on your inputs, you could potentially afford a mortgage loan of approximately
$" + maxLoanAmount.toFixed(2) + ". This suggests a home purchase price of around
$" + estimatedHomePrice.toFixed(2) + ".";
resultDiv.innerHTML += "
This calculation assumes a " + maxDebtToIncomeRatio * 100 + "% Debt-to-Income ratio. Actual loan approval depends on lender underwriting, credit score, and other factors.";
}