Understanding how much house you can afford is a crucial first step in the home-buying process. 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 various factors assessed by lenders, including credit score, employment history, and lender-specific debt-to-income ratio limits.
Your Estimated Mortgage Affordability:
.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;
margin-bottom: 20px;
color: #333;
}
.calculator-inputs {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 15px;
margin-bottom: 20px;
}
.input-group {
display: flex;
flex-direction: column;
}
.input-group label {
margin-bottom: 5px;
font-weight: bold;
color: #555;
}
.input-group input {
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
}
.calculator-container button {
display: block;
width: 100%;
padding: 12px 15px;
background-color: #007bff;
color: white;
border: none;
border-radius: 4px;
font-size: 18px;
cursor: pointer;
transition: background-color 0.3s ease;
margin-bottom: 20px;
}
.calculator-container button:hover {
background-color: #0056b3;
}
.calculator-result {
background-color: #e9ecef;
padding: 15px;
border-radius: 4px;
text-align: center;
}
.calculator-result h3 {
margin-top: 0;
color: #333;
}
#maxLoanAmount, #estimatedMaxHomePrice {
font-size: 1.2em;
font-weight: bold;
color: #28a745;
margin-top: 10px;
}
#note {
font-size: 0.9em;
color: #6c757d;
margin-top: 15px;
}
function calculateMortgageAffordability() {
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 loanTermYears = parseFloat(document.getElementById("loanTermYears").value);
var maxLoanAmountDisplay = document.getElementById("maxLoanAmount");
var estimatedMaxHomePriceDisplay = document.getElementById("estimatedMaxHomePrice");
var noteDisplay = document.getElementById("note");
// Clear previous results and notes
maxLoanAmountDisplay.textContent = "";
estimatedMaxHomePriceDisplay.textContent = "";
noteDisplay.textContent = "";
// Basic validation
if (isNaN(grossMonthlyIncome) || grossMonthlyIncome <= 0 ||
isNaN(monthlyDebtPayments) || monthlyDebtPayments < 0 ||
isNaN(downPayment) || downPayment < 0 ||
isNaN(interestRate) || interestRate <= 0 ||
isNaN(loanTermYears) || loanTermYears <= 0) {
noteDisplay.textContent = "Please enter valid positive numbers for all fields.";
return;
}
// Lender typically allows for a DTI ratio of around 36-43% for PITI (Principal, Interest, Taxes, Insurance)
// For simplicity, we'll use a common guideline for PITI payments not exceeding 36% of gross income.
// We'll also subtract existing debt payments to find the maximum allowable mortgage payment.
var maxDTI = 0.36; // Debt-to-Income Ratio limit for PITI
// Calculate maximum total monthly housing payment (PITI)
var maxPITI = grossMonthlyIncome * maxDTI;
// Calculate maximum monthly mortgage payment (Principal & Interest only)
var maxMortgagePayment = maxPITI – monthlyDebtPayments;
if (maxMortgagePayment 0) {
// Using the annuity formula to solve for Principal (P): M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
// Rearranging for P: P = M [ (1 + i)^n – 1] / [ i(1 + i)^n ]
var numerator = Math.pow(1 + monthlyInterestRate, loanTermMonths) – 1;
var denominator = monthlyInterestRate * Math.pow(1 + monthlyInterestRate, loanTermMonths);
maxLoanAmount = maxMortgagePayment * (numerator / denominator);
} else {
// If interest rate is 0, the loan amount is simply monthly payment * term
maxLoanAmount = maxMortgagePayment * loanTermMonths;
}
var estimatedMaxHomePrice = maxLoanAmount + downPayment;
// Format numbers for display
var formattedMaxLoanAmount = "$" + maxLoanAmount.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
var formattedEstimatedMaxHomePrice = "$" + estimatedMaxHomePrice.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
maxLoanAmountDisplay.textContent = "Estimated Maximum Loan Amount: " + formattedMaxLoanAmount;
estimatedMaxHomePriceDisplay.textContent = "Estimated Maximum Home Price: " + formattedEstimatedMaxHomePrice;
noteDisplay.textContent = "This is an estimate. Actual loan approval depends on lender's criteria, credit score, and other factors. This calculation assumes Principal, Interest, Taxes, and Insurance (PITI) do not exceed 36% of your gross monthly income, minus your existing monthly debts.";
}