Advanced Mortgage Payment Calculator
:root {
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margin: 0;
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.calculator-wrapper {
max-width: 800px;
margin: 0 auto;
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padding: 30px;
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text-align: center;
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.calc-header h2 {
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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
Payoff Date:
–
Total Interest Paid:
$0.00
Understanding Your Mortgage Payment
Using a reliable Mortgage Payment Calculator is the first step in the home buying journey. Whether you are a first-time homebuyer or a real estate investor, knowing exactly how your monthly payment is broken down helps you budget effectively and avoid financial strain.
What is Included in a Mortgage Payment?
Most monthly mortgage payments consist of four main components, often referred to by the acronym PITI:
- Principal: The portion of your payment that reduces the loan balance.
- Interest: The cost of borrowing money from the lender.
- Taxes: Property taxes collected by your local government, often held in escrow by the lender.
- Insurance: Homeowners insurance to protect against damage, also typically held in escrow.
How Interest Rates Affect Your Buying Power
Even a small change in interest rates can significantly impact your monthly payment and the total cost of the loan. For example, on a $300,000 loan, a 1% increase in interest rate can raise your monthly payment by hundreds of dollars and cost tens of thousands more in interest over the life of a 30-year loan.
Principal vs. Interest Over Time
Mortgages use an amortization schedule. In the early years of your loan, the majority of your payment goes toward interest. As time passes and the principal balance decreases, a larger portion of your payment goes toward paying down the principal. This calculator estimates your total interest paid to help you see the long-term cost of borrowing.
Why Include HOA Fees?
If you are buying a condo or a home in a planned community, Homeowners Association (HOA) fees are a mandatory monthly cost. While they are not paid to the lender (and thus don't include interest), lenders factor them into your Debt-to-Income (DTI) ratio when qualifying you for a loan. Always include these in your calculation to get a true picture of affordability.
// Set default date to today
var today = new Date();
var dd = String(today.getDate()).padStart(2, '0');
var mm = String(today.getMonth() + 1).padStart(2, '0');
var yyyy = today.getFullYear();
document.getElementById('startDate').value = yyyy + '-' + mm + '-' + dd;
function formatCurrency(num) {
return new Intl.NumberFormat('en-US', { style: 'currency', currency: 'USD' }).format(num);
}
function calculateMortgage() {
// Get Inputs
var homePrice = parseFloat(document.getElementById("homePrice").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var termYears = parseInt(document.getElementById("loanTerm").value);
var annualTax = parseFloat(document.getElementById("propertyTax").value);
var annualIns = parseFloat(document.getElementById("homeInsurance").value);
var monthlyHOA = parseFloat(document.getElementById("hoaFees").value);
var startDateVal = document.getElementById("startDate").value;
// Validation
if (isNaN(homePrice) || homePrice <= 0) {
alert("Please enter a valid Home Price.");
return;
}
if (isNaN(downPayment) || downPayment < 0) {
downPayment = 0;
}
if (isNaN(interestRate) || interestRate < 0) {
alert("Please enter a valid Interest Rate.");
return;
}
// Calculations
var loanAmount = homePrice – downPayment;
if (loanAmount <= 0) {
alert("Down payment cannot be greater than or equal to home price.");
return;
}
var monthlyInterestRate = (interestRate / 100) / 12;
var numberOfPayments = termYears * 12;
// Mortgage Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var monthlyPI = 0;
if (interestRate === 0) {
monthlyPI = loanAmount / numberOfPayments;
} else {
var mathPower = Math.pow(1 + monthlyInterestRate, numberOfPayments);
monthlyPI = loanAmount * (monthlyInterestRate * mathPower) / (mathPower – 1);
}
var monthlyTax = annualTax / 12;
var monthlyIns = annualIns / 12;
// Total Monthly Payment
var totalMonthlyPayment = monthlyPI + monthlyTax + monthlyIns + monthlyHOA;
// Total Interest
var totalCostOfLoan = monthlyPI * numberOfPayments;
var totalInterest = totalCostOfLoan – loanAmount;
// Payoff Date
var start = new Date(startDateVal);
start.setMonth(start.getMonth() + numberOfPayments);
var options = { year: 'numeric', month: 'long', day: 'numeric' };
var payoffDateString = start.toLocaleDateString('en-US', options);
// Update UI
document.getElementById("monthlyTotalDisplay").innerHTML = formatCurrency(totalMonthlyPayment);
document.getElementById("piDisplay").innerHTML = formatCurrency(monthlyPI);
document.getElementById("taxDisplay").innerHTML = formatCurrency(monthlyTax);
document.getElementById("insDisplay").innerHTML = formatCurrency(monthlyIns);
document.getElementById("hoaDisplay").innerHTML = formatCurrency(monthlyHOA);
document.getElementById("loanAmountDisplay").innerHTML = formatCurrency(loanAmount);
document.getElementById("totalInterestDisplay").innerHTML = formatCurrency(totalInterest);
document.getElementById("payoffDateDisplay").innerHTML = payoffDateString;
// Show Results
document.getElementById("resultSection").style.display = "block";
// Scroll to results
document.getElementById("resultSection").scrollIntoView({ behavior: 'smooth' });
}