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.mc-input { width: 100%; padding: 10px; border: 1px solid #ccc; border-radius: 4px; font-size: 16px; box-sizing: border-box; }
.mc-input:focus { border-color: #0073aa; outline: none; }
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.mc-btn:hover { background-color: #005177; }
.mc-results { margin-top: 30px; background-color: #f9f9f9; padding: 20px; border-radius: 8px; border-left: 5px solid #0073aa; display: none; }
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.mc-error { color: #d63638; display: none; margin-top: 10px; font-weight: bold; }
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function calculateMortgage() {
// Get Input Values
var homePrice = parseFloat(document.getElementById('homePrice').value);
var downPayment = parseFloat(document.getElementById('downPayment').value);
var interestRate = parseFloat(document.getElementById('interestRate').value);
var loanTermYears = parseInt(document.getElementById('loanTerm').value);
var propertyTaxYear = parseFloat(document.getElementById('propertyTax').value);
var homeInsuranceYear = parseFloat(document.getElementById('homeInsurance').value);
// Error Handling
var errorDiv = document.getElementById('mcError');
var resultsDiv = document.getElementById('mortgageResults');
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTermYears) || isNaN(propertyTaxYear) || isNaN(homeInsuranceYear)) {
errorDiv.style.display = 'block';
resultsDiv.style.display = 'none';
return;
} else {
errorDiv.style.display = 'none';
}
// Calculations
var principal = homePrice – downPayment;
// Handle edge case where down payment > home price
if (principal < 0) principal = 0;
var monthlyInterestRate = (interestRate / 100) / 12;
var totalPayments = loanTermYears * 12;
// Monthly PI Calculation
var monthlyPI = 0;
if (interestRate === 0) {
monthlyPI = principal / totalPayments;
} else {
var x = Math.pow(1 + monthlyInterestRate, totalPayments);
monthlyPI = (principal * x * monthlyInterestRate) / (x – 1);
}
// Escrow (Tax + Insurance)
var monthlyTax = propertyTaxYear / 12;
var monthlyInsurance = homeInsuranceYear / 12;
var monthlyEscrow = monthlyTax + monthlyInsurance;
var totalMonthlyPayment = monthlyPI + monthlyEscrow;
var totalInterest = (monthlyPI * totalPayments) – principal;
var totalCost = principal + totalInterest;
// Display Results (Formatting as Currency)
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
document.getElementById('resPrincipalInterest').innerHTML = formatter.format(monthlyPI);
document.getElementById('resTaxIns').innerHTML = formatter.format(monthlyEscrow);
document.getElementById('resTotalMonthly').innerHTML = formatter.format(totalMonthlyPayment);
document.getElementById('resLoanAmount').innerHTML = formatter.format(principal);
document.getElementById('resTotalInterest').innerHTML = formatter.format(totalInterest);
document.getElementById('resTotalCost').innerHTML = formatter.format(totalCost);
// Show Results
resultsDiv.style.display = 'block';
}
Mortgage Payment Calculator
30 Years
20 Years
15 Years
10 Years
Please enter valid numbers for all fields.
Monthly Principal & Interest:
$0.00
Monthly Tax & Insurance:
$0.00
Total Monthly Payment:
$0.00
Total Loan Amount:
$0.00
Total Interest Paid:
$0.00
Total Cost (Loan + Interest):
$0.00
Understanding Your Mortgage Calculation
Purchasing a home is likely the largest financial decision you will make in your lifetime. Understanding exactly how your mortgage payments are calculated is essential for budgeting and long-term financial planning. This calculator helps you break down the monthly costs associated with homeownership.
How Mortgage Payments Are Calculated
A standard mortgage payment typically consists of four main components, often referred to as PITI:
- Principal: The portion of your payment that goes toward paying down the original loan amount. In the early years of a mortgage, this amount is small but grows over time.
- Interest: The fee charged by the lender for borrowing the money. Initially, interest makes up the majority of your monthly payment.
- Taxes: Property taxes assessed by your local government, often collected by the lender in an escrow account and paid annually on your behalf.
- Insurance: Homeowners insurance protects your property against damage. Like taxes, this is often divided into monthly installments and held in escrow.
The Amortization Formula
The core calculation for the Principal and Interest (PI) portion uses the standard amortization formula:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
Where:
- M = Total monthly payment
- P = Principal loan amount
- i = Monthly interest rate (Annual rate / 12)
- n = Number of months required to repay the loan
Factors Affecting Your Monthly Payment
Several variables can significantly impact how much you pay every month:
- Down Payment: A larger down payment reduces the principal loan amount, which lowers both your monthly payment and the total interest paid over the life of the loan. If you put down less than 20%, you may also be required to pay Private Mortgage Insurance (PMI), which increases costs.
- Loan Term: A 30-year term offers lower monthly payments but results in higher total interest costs compared to a 15-year term. Shorter terms save money in the long run but require higher monthly cash flow.
- Interest Rate: Even a fraction of a percentage point difference in your interest rate can save or cost you tens of thousands of dollars over the life of the loan. Improving your credit score is one of the best ways to secure a lower rate.
Why Include Taxes and Insurance?
Many online calculators only show the Principal and Interest. However, most lenders require an escrow account, meaning your actual check written to the bank includes taxes and insurance. This calculator includes these estimates to give you a realistic view of your "out-of-pocket" monthly housing expense.