Mortgage Calculator with Taxes & Insurance
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line-height: 1.6;
color: var(–text-color);
background-color: var(–bg-color);
margin: 0;
padding: 20px;
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.calculator-container {
max-width: 900px;
margin: 0 auto;
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border-radius: 12px;
box-shadow: 0 4px 15px rgba(0,0,0,0.1);
overflow: hidden;
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.calc-header {
background: var(–primary-color);
color: #fff;
padding: 20px;
text-align: center;
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.calc-header h1 { margin: 0; font-size: 24px; }
.calc-body {
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grid-template-columns: 1fr 1fr;
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@media (max-width: 768px) {
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input[type="number"] {
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Estimated Monthly Payment
$0.00
Principal & Interest
$0.00
Property Tax (Monthly)
$0.00
Home Insurance (Monthly)
$0.00
HOA Fees
$0.00
Total Loan Amount
$0.00
Total Interest Paid
$0.00
Total Cost of Loan
$0.00
Payoff Date
–
Understanding Your Mortgage Payment
Buying a home is one of the most significant financial decisions you will make. This Mortgage Calculator is designed to help you understand exactly what your monthly financial commitment will look like. Unlike basic calculators that only show Principal and Interest, this tool factors in the "hidden" costs of homeownership: Property Taxes, Homeowners Insurance, and HOA fees.
How the Formula Works
Your monthly mortgage payment is primarily composed of four parts, often referred to as PITI:
- Principal: The portion of your payment that goes toward reducing the loan balance. In the early years of a mortgage, this amount is small.
- Interest: The cost of borrowing money. At the start of your loan term, interest makes up the majority of your payment.
- Taxes: Property taxes assessed by your local government, usually collected by your lender in an escrow account.
- Insurance: Homeowners insurance to protect against damage, also typically paid via escrow.
Why Your Interest Rate Matters
Even a small difference in your interest rate can have a massive impact on your total loan cost. For example, on a $300,000 loan, a 1% difference in interest rate can save or cost you tens of thousands of dollars over the life of a 30-year loan. Use the calculator to experiment with different rates to see how improving your credit score could save you money.
Principal & Interest Calculation Logic
We use the standard amortization formula to calculate your monthly Principal & Interest (P&I):
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
- M = Total monthly payment
- P = Principal loan amount
- i = Monthly interest rate
- n = Number of months required to repay the loan
Tips for Lowering Your Payment
If the estimated monthly payment is higher than your budget allows, consider these strategies:
- Increase your Down Payment: This reduces the Principal (P), which lowers the monthly payment and reduces total interest paid.
- Eliminate PMI: If you put down less than 20%, you may be paying Private Mortgage Insurance. Saving for a 20% down payment removes this cost.
- Shop for Insurance: Homeowners insurance rates vary. Shopping around can lower your monthly escrow requirement.
function calculateMortgage() {
// 1. Get Input Values
var homePrice = parseFloat(document.getElementById("homePrice").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var annualRate = parseFloat(document.getElementById("interestRate").value);
var years = parseFloat(document.getElementById("loanTerm").value);
var yearlyTax = parseFloat(document.getElementById("propertyTax").value);
var yearlyIns = parseFloat(document.getElementById("homeInsurance").value);
var monthlyHOA = parseFloat(document.getElementById("hoaFees").value);
// 2. Validation
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(annualRate) || isNaN(years)) {
alert("Please enter valid numbers for Home Price, Down Payment, Interest Rate, and Loan Term.");
return;
}
// Handle empty optional fields
if (isNaN(yearlyTax)) yearlyTax = 0;
if (isNaN(yearlyIns)) yearlyIns = 0;
if (isNaN(monthlyHOA)) monthlyHOA = 0;
// 3. Core Calculations
var principal = homePrice – downPayment;
// Prevent negative principal
if (principal <= 0) {
document.getElementById("totalMonthlyPayment").innerHTML = "$0.00";
alert("Down payment cannot be greater than or equal to Home Price.");
return;
}
var monthlyRate = (annualRate / 100) / 12;
var numberOfPayments = years * 12;
// Calculate Monthly Principal & Interest (P&I)
// Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var monthlyPI = 0;
if (annualRate === 0) {
monthlyPI = principal / numberOfPayments;
} else {
monthlyPI = (principal * monthlyRate) / (1 – Math.pow(1 + monthlyRate, -numberOfPayments));
}
// Calculate Escrow items (Tax + Insurance)
var monthlyTaxPayment = yearlyTax / 12;
var monthlyInsPayment = yearlyIns / 12;
// Total Monthly Payment
var totalMonthly = monthlyPI + monthlyTaxPayment + monthlyInsPayment + monthlyHOA;
// Total Lifetime Costs
var totalPrincipalAndInterest = monthlyPI * numberOfPayments;
var totalInterestOnly = totalPrincipalAndInterest – principal;
var totalCostOfLoan = totalPrincipalAndInterest + (monthlyTaxPayment * numberOfPayments) + (monthlyInsPayment * numberOfPayments) + (monthlyHOA * numberOfPayments);
// Calculate Payoff Date
var today = new Date();
var payoffDate = new Date(today.setMonth(today.getMonth() + numberOfPayments));
var options = { month: 'long', year: 'numeric' };
var payoffString = payoffDate.toLocaleDateString('en-US', options);
// 4. Formatting Currency
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
// 5. Update UI
document.getElementById("totalMonthlyPayment").innerHTML = formatter.format(totalMonthly);
document.getElementById("monthlyPI").innerHTML = formatter.format(monthlyPI);
document.getElementById("monthlyTax").innerHTML = formatter.format(monthlyTaxPayment);
document.getElementById("monthlyIns").innerHTML = formatter.format(monthlyInsPayment);
document.getElementById("displayHOA").innerHTML = formatter.format(monthlyHOA);
document.getElementById("totalLoanAmount").innerHTML = formatter.format(principal);
document.getElementById("totalInterest").innerHTML = formatter.format(totalInterestOnly);
document.getElementById("totalCost").innerHTML = formatter.format(totalCostOfLoan);
document.getElementById("payoffDate").innerHTML = payoffString;
}
// Run calculation on load to show initial valid state
window.onload = function() {
calculateMortgage();
};