Estimate your monthly payments, including taxes and insurance.
30 Years
20 Years
15 Years
10 Years
Please enter valid positive numbers for all fields.
Monthly Principal & Interest:$0.00
Monthly Tax & Insurance:$0.00
Total Monthly Payment:$0.00
Total Interest Paid:$0.00
Total Cost of Loan:$0.00
Understanding Your Mortgage Calculation
Buying a home is one of the most significant financial decisions you will make. This Mortgage Payment Calculator helps you understand the true monthly cost of homeownership by factoring in not just the principal and interest, but also the critical components of property taxes and homeowners insurance.
Principal and Interest (P&I)
The core of your mortgage payment consists of Principal and Interest. Principal is the money that goes towards paying off the original loan amount. Interest is the cost of borrowing that money. In the early years of a mortgage (especially a 30-year term), a large portion of your payment goes toward interest, while in later years, more goes toward the principal.
The Impact of Down Payments
Your down payment significantly affects your monthly obligations. A larger down payment reduces the loan principal, which lowers your monthly P&I payment and the total interest paid over the life of the loan. For example, putting 20% down often eliminates the need for Private Mortgage Insurance (PMI), saving you hundreds of dollars monthly.
Taxes and Insurance (Escrow)
Most lenders require an escrow account for Property Taxes and Homeowners Insurance.
Property Tax: Assessed by your local government based on property value.
Homeowners Insurance: Protects your property against damage and liability.
These annual costs are divided by 12 and added to your monthly mortgage bill.
How Interest Rates Affect Affordability
Even a small fluctuation in interest rates can drastically change your buying power. On a $400,000 loan, a 1% increase in interest rate can add hundreds of dollars to your monthly payment and tens of thousands to the total cost of the loan over 30 years.
Using This Calculator
Enter the home price, your planned down payment, the current interest rate, and the loan term. Don't forget to estimate annual taxes and insurance for a realistic monthly figure. This tool provides a comprehensive breakdown to help you budget effectively for your new home.
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 loanTerm = parseFloat(document.getElementById('loanTerm').value);
var propertyTax = parseFloat(document.getElementById('propertyTax').value);
var homeInsurance = parseFloat(document.getElementById('homeInsurance').value);
var errorMsg = document.getElementById('errorMsg');
var resultBox = document.getElementById('resultBox');
// Validation
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTerm) || homePrice <= 0) {
errorMsg.style.display = 'block';
resultBox.style.display = 'none';
return;
} else {
errorMsg.style.display = 'none';
}
// Handle optional fields with defaults if empty
if (isNaN(propertyTax)) propertyTax = 0;
if (isNaN(homeInsurance)) homeInsurance = 0;
// Core Calculation
var principal = homePrice – downPayment;
if (principal <= 0) {
errorMsg.innerText = "Down payment cannot be greater than or equal to Home Price.";
errorMsg.style.display = 'block';
resultBox.style.display = 'none';
return;
}
// Monthly Interest Rate
var monthlyRate = (interestRate / 100) / 12;
// Total Number of Payments
var numberOfPayments = loanTerm * 12;
// Calculate Monthly P&I
var monthlyPI = 0;
if (interestRate === 0) {
monthlyPI = principal / numberOfPayments;
} else {
// Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
monthlyPI = (principal * monthlyRate * Math.pow(1 + monthlyRate, numberOfPayments)) / (Math.pow(1 + monthlyRate, numberOfPayments) – 1);
}
// Calculate Escrow (Tax + Insurance monthly)
var monthlyTax = propertyTax / 12;
var monthlyInsurance = homeInsurance / 12;
var totalEscrow = monthlyTax + monthlyInsurance;
// Totals
var totalMonthlyPayment = monthlyPI + totalEscrow;
var totalPaymentOverLife = (monthlyPI * numberOfPayments);
var totalInterestPaid = totalPaymentOverLife – principal;
// Display Results with formatting
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
document.getElementById('monthlyPI').innerText = formatter.format(monthlyPI);
document.getElementById('monthlyEscrow').innerText = formatter.format(totalEscrow);
document.getElementById('totalMonthly').innerText = formatter.format(totalMonthlyPayment);
document.getElementById('totalInterest').innerText = formatter.format(totalInterestPaid);
document.getElementById('totalCost').innerText = formatter.format(totalPaymentOverLife + (totalEscrow * numberOfPayments));
// Show Results
resultBox.style.display = 'block';
}