Understanding how much you can afford for a mortgage is a crucial first step in the home-buying process. This calculator helps you estimate your maximum affordable mortgage payment based on your income, debts, and desired loan terms. Remember, this is an estimate, and lenders will have their own specific criteria.
.calculator-container {
font-family: Arial, 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 {
color: #555;
line-height: 1.6;
margin-bottom: 20px;
}
.calculator-inputs {
display: grid;
grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
gap: 15px;
margin-bottom: 20px;
}
.input-group {
display: flex;
flex-direction: column;
}
.input-group label {
margin-bottom: 5px;
font-weight: bold;
color: #444;
}
.input-group input {
padding: 8px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 1rem;
}
.calculator-container button {
background-color: #4CAF50;
color: white;
padding: 10px 15px;
border: none;
border-radius: 4px;
cursor: pointer;
font-size: 1rem;
width: 100%;
transition: background-color 0.3s ease;
}
.calculator-container button:hover {
background-color: #45a049;
}
#result {
margin-top: 20px;
padding: 15px;
border: 1px solid #e0e0e0;
background-color: #fff;
border-radius: 4px;
text-align: center;
font-size: 1.1rem;
color: #333;
}
#result strong {
color: #4CAF50;
}
function calculateMortgageAffordability() {
var grossMonthlyIncome = parseFloat(document.getElementById("grossMonthlyIncome").value);
var existingDebts = parseFloat(document.getElementById("existingDebts").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var annualInterestRate = 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 pmiAnnual = parseFloat(document.getElementById("pmiAnnual").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
// Input validation
if (isNaN(grossMonthlyIncome) || grossMonthlyIncome <= 0 ||
isNaN(existingDebts) || existingDebts < 0 ||
isNaN(downPayment) || downPayment < 0 ||
isNaN(annualInterestRate) || annualInterestRate <= 0 ||
isNaN(loanTermYears) || loanTermYears <= 0 ||
isNaN(propertyTaxesAnnual) || propertyTaxesAnnual < 0 ||
isNaN(homeownersInsuranceAnnual) || homeownersInsuranceAnnual < 0 ||
isNaN(pmiAnnual) || pmiAnnual < 0) {
resultDiv.innerHTML = "Error: Please enter valid positive numbers for all fields.";
return;
}
// Lender debt-to-income ratio guidelines (common but can vary)
// Typically lenders look at Front-End Ratio (PITI/Gross Income) and Back-End Ratio ((PITI + Debts)/Gross Income)
// A common guideline is a back-end DTI of 36-43%. Let's use 43% as an example.
var maxBackEndDTI = 0.43; // 43%
// Calculate maximum allowed total monthly housing payment (PITI + PMI)
var maxTotalHousingPayment = (grossMonthlyIncome * maxBackEndDTI) – existingDebts;
if (maxTotalHousingPayment <= 0) {
resultDiv.innerHTML = "Based on your income and debts, your affordable housing payment is too low to qualify for a mortgage.";
return;
}
var monthlyInterestRate = annualInterestRate / 100 / 12;
var numberOfPayments = loanTermYears * 12;
// Calculate maximum loan amount based on max PITI (Principal, Interest, Taxes, Insurance)
// We need to work backwards from the maximum total housing payment.
// Max PITI = Max Total Housing Payment – Monthly Taxes – Monthly Insurance – Monthly PMI
var monthlyPropertyTaxes = propertyTaxesAnnual / 12;
var monthlyHomeownersInsurance = homeownersInsuranceAnnual / 12;
var monthlyPMI = pmiAnnual / 12;
var maxPITI = maxTotalHousingPayment – monthlyPropertyTaxes – monthlyHomeownersInsurance – monthlyPMI;
if (maxPITI 0) {
var numerator = Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1;
var denominator = monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments);
maxLoanAmount = maxPITI * (numerator / denominator);
} else {
// Handle zero interest rate case (though unlikely for mortgages)
maxLoanAmount = maxPITI * numberOfPayments;
}
var estimatedMaxHomePrice = maxLoanAmount + downPayment;
resultDiv.innerHTML = "Estimated Maximum Affordable Home Price: $" + estimatedMaxHomePrice.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,') + "" +
"Estimated Maximum Loan Amount: $" + maxLoanAmount.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,') + "" +
"Estimated Maximum PITI Payment: $" + maxPITI.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,') + " (Principal, Interest, Taxes, Insurance)";
}