Estimate your monthly mortgage payments including taxes and insurance.
30 Years
20 Years
15 Years
10 Years
Principal & Interest:–
Monthly Property Tax:–
Monthly Home Insurance:–
Total Monthly Payment:–
Total Interest Over Loan:–
function calculateMortgage() {
// Get input values using var
var homePrice = parseFloat(document.getElementById('mcHomePrice').value);
var downPayment = parseFloat(document.getElementById('mcDownPayment').value);
var interestRate = parseFloat(document.getElementById('mcInterestRate').value);
var loanTerm = parseInt(document.getElementById('mcLoanTerm').value);
var propertyTax = parseFloat(document.getElementById('mcPropertyTax').value);
var homeInsurance = parseFloat(document.getElementById('mcHomeInsurance').value);
// Validate inputs
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTerm)) {
alert("Please enter valid numbers for all fields.");
return;
}
// Handle optional fields for tax and insurance (default to 0 if empty/NaN)
if (isNaN(propertyTax)) propertyTax = 0;
if (isNaN(homeInsurance)) homeInsurance = 0;
// Loan Principal
var principal = homePrice – downPayment;
if (principal <= 0) {
alert("Down payment cannot be greater than or equal to the home price.");
return;
}
// Monthly Interest Rate
var monthlyRate = (interestRate / 100) / 12;
// Total Number of Payments
var numberOfPayments = loanTerm * 12;
// Calculate Principal & Interest Payment (Standard Amortization Formula)
// M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var monthlyPrincipalInterest = 0;
if (interestRate === 0) {
monthlyPrincipalInterest = principal / numberOfPayments;
} else {
monthlyPrincipalInterest = principal * ( (monthlyRate * Math.pow(1 + monthlyRate, numberOfPayments)) / (Math.pow(1 + monthlyRate, numberOfPayments) – 1) );
}
// Calculate Monthly Tax and Insurance
var monthlyTax = propertyTax / 12;
var monthlyInsurance = homeInsurance / 12;
// Total Monthly Payment
var totalMonthlyPayment = monthlyPrincipalInterest + monthlyTax + monthlyInsurance;
// Total Interest Paid over Life of Loan
var totalRepayment = (monthlyPrincipalInterest * numberOfPayments);
var totalInterest = totalRepayment – principal;
// Update the DOM
document.getElementById('resPrincipalInterest').innerText = "$" + monthlyPrincipalInterest.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
document.getElementById('resTax').innerText = "$" + monthlyTax.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
document.getElementById('resInsurance').innerText = "$" + monthlyInsurance.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
document.getElementById('resTotal').innerText = "$" + totalMonthlyPayment.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
document.getElementById('resTotalInterest').innerText = "$" + totalInterest.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
// Show Results
document.getElementById('mcResults').style.display = 'block';
}
Understanding Your Mortgage Calculation
Buying a home is one of the largest financial decisions you will make. Using a mortgage calculator is an essential step in the home-buying process, allowing you to estimate your monthly financial commitment accurately. This tool breaks down the components of your monthly payment, including principal, interest, taxes, and insurance (often referred to as PITI).
How is Your Monthly Payment Calculated?
The core of your mortgage payment is determined by the amortization formula, which calculates the amount needed to pay off your loan balance over a set period (the loan term) at a specific interest rate. Here are the key variables:
Principal: This is the money you borrow from the lender. It is calculated as the Home Price minus your Down Payment.
Interest Rate: The cost of borrowing money, expressed as an annual percentage. Even a small difference in rates can significantly impact your monthly payment and the total interest paid over the life of the loan.
Loan Term: The duration of the loan. A 30-year term typically offers lower monthly payments but results in higher total interest costs compared to a 15-year term.
The Impact of Escrow: Taxes and Insurance
Many first-time homebuyers focus solely on the principal and interest payment, forgetting that property ownership comes with additional recurring costs. Lenders often require you to pay these into an escrow account monthly.
Property Taxes: These are levied by your local government based on the assessed value of your home. They fund local services like schools and roads. This calculator estimates the monthly portion of your annual tax bill.
Homeowners Insurance: This protects your property against damage and liability. Like taxes, the annual premium is usually divided by 12 and added to your monthly mortgage payment.
Example Calculation
Let's say you purchase a home for $350,000 with a $70,000 (20%) down payment. This leaves a loan amount of $280,000.
If you secure a 30-year fixed-rate mortgage at 6.5%:
Your Principal & Interest payment would be approximately $1,769.
If your annual property taxes are $4,000, add $333/month.
If your annual insurance is $1,200, add $100/month.
Total Estimated Payment: $2,202 / month.
Why Use This Calculator?
By inputting different scenarios—such as a higher down payment or a lower interest rate—you can see exactly how these changes affect your bottom line. This empowers you to budget effectively and negotiate better terms with lenders.