.calculator-container h2 { text-align: center; color: #333; }
.form-group { margin-bottom: 15px; }
.form-group label { display: block; margin-bottom: 5px; font-weight: bold; color: #555; }
.form-group input { width: 100%; padding: 10px; border: 1px solid #ccc; border-radius: 4px; box-sizing: border-box; } /* Added box-sizing */
.calc-button { width: 100%; padding: 12px; background-color: #0073aa; color: white; border: none; border-radius: 4px; font-size: 16px; cursor: pointer; transition: background-color 0.3s; }
.calc-button:hover { background-color: #005177; }
#mortgage-results { margin-top: 25px; padding: 20px; background-color: #eef7fb; border-left: 5px solid #0073aa; display: none; }
.result-line { display: flex; justify-content: space-between; margin-bottom: 10px; font-size: 16px; }
.result-line.main-result { font-size: 20px; font-weight: bold; color: #0073aa; border-bottom: 1px solid #d0e4f0; padding-bottom: 10px; margin-bottom: 15px; }
.error-message { color: #d32f2f; background-color: #fdecea; padding: 10px; border-radius: 4px; margin-bottom: 15px; display: none; }
function calculateMortgage() {
var homePriceInput = document.getElementById("homePrice");
var downPaymentInput = document.getElementById("downPayment");
var interestRateInput = document.getElementById("interestRate");
var loanTermInput = document.getElementById("loanTerm");
var resultsDiv = document.getElementById("mortgage-results");
var errorDiv = document.getElementById("calc-error");
// Reset previous results and errors
resultsDiv.style.display = "none";
errorDiv.style.display = "none";
errorDiv.innerHTML = "";
// Parse inputs
var homePrice = parseFloat(homePriceInput.value);
var downPayment = parseFloat(downPaymentInput.value);
var annualRatePercentage = parseFloat(interestRateInput.value);
var loanTermYears = parseInt(loanTermInput.value);
// Validate inputs
if (isNaN(homePrice) || homePrice <= 0 ||
isNaN(annualRatePercentage) || annualRatePercentage < 0 ||
isNaN(loanTermYears) || loanTermYears <= 0) {
errorDiv.innerHTML = "Please enter valid positive numbers for Home Price, Interest Rate, and Loan Term.";
errorDiv.style.display = "block";
return;
}
if (isNaN(downPayment) || downPayment < 0) {
downPayment = 0; // Assume 0 if empty or invalid
}
var principal = homePrice – downPayment;
if (principal <= 0) {
errorDiv.innerHTML = "Your down payment is equal to or greater than the home price. You do not need a mortgage.";
errorDiv.style.display = "block";
return;
}
// Calculation Logic
var monthlyRate = (annualRatePercentage / 100) / 12;
var totalPayments = loanTermYears * 12;
var monthlyPayment;
// Handle zero interest rate edge case
if (monthlyRate === 0) {
monthlyPayment = principal / totalPayments;
} else {
// Standard amortization formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
monthlyPayment = principal * (monthlyRate * Math.pow(1 + monthlyRate, totalPayments)) / (Math.pow(1 + monthlyRate, totalPayments) – 1);
}
var totalCost = monthlyPayment * totalPayments;
var totalInterest = totalCost – principal;
// Formatting helper function
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
// Display Results
document.getElementById("monthlyPaymentResult").innerHTML = formatter.format(monthlyPayment);
document.getElementById("totalLoanResult").innerHTML = formatter.format(principal);
document.getElementById("totalInterestResult").innerHTML = formatter.format(totalInterest);
document.getElementById("totalCostResult").innerHTML = formatter.format(totalCost);
resultsDiv.style.display = "block";
}
Mortgage Payment Calculator
Your Mortgage Estimations
Monthly Principal & Interest:
$0.00
Total Loan Amount:
$0.00
Total Interest Paid Over Life of Loan:
$0.00
Total Cost (Principal + Interest):
$0.00
Understanding Your Mortgage Estimation
Buying a home is likely the largest financial transaction of your life. Understanding how your mortgage payment is calculated is crucial for budgeting and long-term financial planning. This tool helps you estimate your monthly "Principal and Interest" (P&I) obligations based on standard amortization formulas.
Key Mortgage Factors Explained
- Home Price & Down Payment: The starting point. Your loan amount (the "principal") is the Home Price minus your Down Payment. A larger down payment reduces your principal, which lowers your monthly payment and the total interest paid over time.
- Interest Rate: This is the cost of borrowing money, expressed as an annual percentage. Even a small difference in interest rates (e.g., 6.5% vs. 7.0%) can add up to tens of thousands of dollars in extra costs over a 30-year period.
- Loan Term: The duration of the loan. A 30-year term is standard, offering lower monthly payments but higher total interest costs. A 15-year term has higher monthly payments, but you build equity faster and pay significantly less interest over the life of the loan.
What This Calculator Does Not Include
It is important to note that the result provided above is for Principal and Interest only. Your actual monthly housing payment will almost certainly be higher because lenders typically require you to escrow funds for:
- Property Taxes: Levied by your local government, based on the assessed value of your home.
- Homeowners Insurance: Required to protect the asset against damage.
- Private Mortgage Insurance (PMI): Usually required if your down payment is less than 20% of the home's purchase price.
- HOA Fees: If you buy a condo or a home in a managed community.
Use this figure as a baseline and consult with a mortgage professional for a complete loan estimate that includes these additional costs.