Estimate your monthly payments including taxes and insurance.
30 Years
20 Years
15 Years
10 Years
Please check your inputs. Values must be positive.
Principal & Interest:$0.00
Monthly Property Tax:$0.00
Monthly Home Insurance:$0.00
Total Monthly Payment:$0.00
Total Interest Paid over Loan:$0.00
Payoff Date:–
function calculateMortgage() {
// 1. Retrieve Input Values
var price = parseFloat(document.getElementById('homePrice').value);
var down = parseFloat(document.getElementById('downPayment').value);
var rate = parseFloat(document.getElementById('interestRate').value);
var term = parseFloat(document.getElementById('loanTerm').value);
var tax = parseFloat(document.getElementById('propertyTax').value);
var insurance = parseFloat(document.getElementById('homeInsurance').value);
var errorDiv = document.getElementById('errorMsg');
var resultsDiv = document.getElementById('resultsArea');
// 2. Validation
if (isNaN(price) || isNaN(down) || isNaN(rate) || isNaN(term) || isNaN(tax) || isNaN(insurance) || price = price) {
errorDiv.innerText = "Down payment cannot be greater than or equal to Home Price.";
errorDiv.style.display = 'block';
resultsDiv.style.display = 'none';
return;
}
errorDiv.style.display = 'none';
// 3. Calculation Logic
var principal = price – down;
var monthlyRate = (rate / 100) / 12;
var numberOfPayments = term * 12;
// Calculate Principal & Interest (Standard Amortization Formula)
// M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var monthlyPI = 0;
if (rate === 0) {
monthlyPI = principal / numberOfPayments;
} else {
var mathPower = Math.pow(1 + monthlyRate, numberOfPayments);
monthlyPI = principal * ((monthlyRate * mathPower) / (mathPower – 1));
}
// Calculate Escrow items (Tax and Insurance)
var monthlyTax = tax / 12;
var monthlyInsurance = insurance / 12;
// Total Monthly Payment
var totalMonthlyPayment = monthlyPI + monthlyTax + monthlyInsurance;
// Total Interest over life of loan
var totalPaymentOverLife = monthlyPI * numberOfPayments;
var totalInterest = totalPaymentOverLife – principal;
// Calculate Payoff Date
var today = new Date();
var payoffDate = new Date(today.setMonth(today.getMonth() + numberOfPayments));
var options = { year: 'numeric', month: 'long' };
var payoffString = payoffDate.toLocaleDateString('en-US', options);
// 4. Update DOM Results
// Helper function for currency formatting
function formatCurrency(num) {
return '$' + num.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
}
document.getElementById('resPI').innerText = formatCurrency(monthlyPI);
document.getElementById('resTax').innerText = formatCurrency(monthlyTax);
document.getElementById('resIns').innerText = formatCurrency(monthlyInsurance);
document.getElementById('resTotal').innerText = formatCurrency(totalMonthlyPayment);
document.getElementById('resTotalInterest').innerText = formatCurrency(totalInterest);
document.getElementById('resPayoffDate').innerText = payoffString;
// Show Results
resultsDiv.style.display = 'block';
}
Understanding Your Mortgage Payment
Buying a home is one of the most significant financial decisions you will make in your lifetime. Understanding exactly how your monthly mortgage payment is calculated is crucial for maintaining your budget and financial health. This Mortgage Payment Calculator helps you break down the costs associated with your loan, including principal, interest, taxes, and insurance (often referred to as PITI).
How the Mortgage Calculation Works
While the formula might seem complex, the components of a mortgage payment are straightforward. The calculator above uses the standard amortization formula used by lenders across the globe. Here is what goes into the calculation:
Principal: This is the money you borrowed. For example, if you buy a home for $350,000 and put $70,000 down, your principal balance is $280,000. Each month, a portion of your payment goes toward reducing this balance.
Interest: This is the cost of borrowing money. In the early years of a mortgage, the majority of your payment goes toward interest. As the principal balance decreases, the interest portion of your payment also decreases.
Escrow (Taxes & Insurance): Most lenders require you to pay 1/12th of your estimated annual property taxes and homeowners insurance each month. These funds are held in an escrow account and paid on your behalf when due.
The Impact of Interest Rates and Loan Terms
Small changes in your interest rate or loan term can have a dramatic effect on your monthly payment and the total cost of the loan.
Interest Rates
A difference of just 1% in your interest rate can save or cost you tens of thousands of dollars over the life of a 30-year loan. For example, on a $300,000 loan, a 6% rate results in a monthly principal and interest payment of roughly $1,799. If that rate rises to 7%, the payment jumps to $1,996—an increase of nearly $200 per month and over $70,000 in total interest over 30 years.
Loan Term: 15-Year vs. 30-Year
Choosing a shorter loan term, like a 15-year mortgage, will increase your monthly payment because you are paying off the principal faster. However, it significantly reduces the total interest paid. A 30-year term offers lower monthly payments, which improves affordability, but results in higher total interest costs.
What is PMI?
If your down payment is less than 20% of the home price, lenders generally require Private Mortgage Insurance (PMI). This protects the lender if you default on the loan. While this calculator focuses on PITI, remember that PMI can add 0.5% to 1% of the loan amount annually to your costs until you reach 20% equity.
How to Use This Calculator
Enter Home Price: The total purchase price of the property.
Enter Down Payment: The cash you are paying upfront. The more you put down, the lower your monthly payment.
Input Interest Rate: Enter the current annual interest rate offered by your lender.
Select Loan Term: Choose how many years you have to repay the loan (usually 15 or 30).
Taxes & Insurance: Enter the estimated yearly property tax and home insurance costs to get a realistic "out-the-door" monthly payment.
Use this tool to experiment with different scenarios. See how an extra $5,000 in down payment affects your monthly budget, or how shopping around for a lower insurance rate can save you money every month.