Understanding how much mortgage you can afford is a crucial step in the home-buying process. This calculator helps you estimate your maximum affordable mortgage amount based on your income, debts, and estimated interest rates. It's important to remember that this is an estimation, and your actual mortgage approval will depend on lender-specific criteria, credit score, down payment, and market conditions.
.calculator-container {
font-family: sans-serif;
border: 1px solid #ddd;
padding: 20px;
border-radius: 8px;
max-width: 600px;
margin: 20px auto;
background-color: #f9f9f9;
}
.calculator-container h2 {
text-align: center;
margin-bottom: 15px;
color: #333;
}
.calculator-container p {
font-size: 0.9em;
color: #555;
line-height: 1.5;
margin-bottom: 25px;
}
.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: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 1em;
}
.calculator-container button {
display: block;
width: 100%;
padding: 12px 20px;
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: 25px;
padding: 15px;
background-color: #e9ecef;
border: 1px solid #ced4da;
border-radius: 4px;
text-align: center;
font-size: 1.1em;
color: #333;
min-height: 50px;
}
function calculateMortgageAffordability() {
var annualIncome = parseFloat(document.getElementById("annualIncome").value);
var monthlyDebt = parseFloat(document.getElementById("monthlyDebt").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var loanTerm = parseFloat(document.getElementById("loanTerm").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
if (isNaN(annualIncome) || isNaN(monthlyDebt) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTerm) ||
annualIncome < 0 || monthlyDebt < 0 || downPayment < 0 || interestRate < 0 || loanTerm <= 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
// General guideline: Debt-to-Income (DTI) ratio should not exceed 43% for mortgage.
// This calculator uses a simplified approach based on common lender recommendations.
// A common rule of thumb is that total housing costs (PITI – Principal, Interest, Taxes, Insurance)
// should not exceed 28% of gross monthly income, and total debt (including PITI)
// should not exceed 36% of gross monthly income. We'll use the 36% as a starting point for total debt.
var grossMonthlyIncome = annualIncome / 12;
var maxTotalMonthlyDebtPayment = grossMonthlyIncome * 0.36; // 36% DTI
var maxMortgagePayment = maxTotalMonthlyDebtPayment – monthlyDebt;
if (maxMortgagePayment 0 && numberOfPayments > 0) {
// Rearrange the formula to solve for P:
// P = M [ (1 + i)^n – 1] / [ i(1 + i)^n ]
var factor = Math.pow(1 + monthlyInterestRate, numberOfPayments);
maxLoanAmount = maxMortgagePayment * (factor – 1) / (monthlyInterestRate * factor);
} else if (monthlyInterestRate === 0 && numberOfPayments > 0) {
// Handle 0 interest rate case (unlikely for mortgages but for completeness)
maxLoanAmount = maxMortgagePayment * numberOfPayments;
} else {
resultDiv.innerHTML = "Invalid interest rate or loan term for calculation.";
return;
}
var estimatedMortgageAmount = maxLoanAmount;
var affordableHomePrice = estimatedMortgageAmount + downPayment;
resultDiv.innerHTML =
"Estimated Maximum Mortgage Amount: $" + estimatedMortgageAmount.toLocaleString(undefined, { minimumFractionDigits: 0, maximumFractionDigits: 0 }) + "" +
"Estimated Affordable Home Price (with down payment): $" + affordableHomePrice.toLocaleString(undefined, { minimumFractionDigits: 0, maximumFractionDigits: 0 }) + "";
}