Calculate your estimated monthly mortgage payment, including principal and interest.
Your Estimated Monthly Payment
$0.00
Total Paid: $0.00
Total Interest: $0.00
Understanding Your Mortgage Payment
A mortgage is a significant financial commitment, and understanding how your monthly payment is calculated is crucial. This calculator estimates the principal and interest (P&I) portion of your monthly mortgage payment. It does not include other costs like property taxes, homeowner's insurance, or private mortgage insurance (PMI), which are often escrowed and paid as part of your total housing expense.
How the Calculation Works
The standard formula for calculating a fixed-rate mortgage payment is:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
Where:
M = Your total monthly mortgage payment (Principal & Interest)
P = The principal loan amount (the amount you borrow)
i = Your monthly interest rate (annual interest rate divided by 12)
n = The total number of payments over the loan's lifetime (loan term in years multiplied by 12)
Example Calculation
Let's say you are taking out a mortgage with the following details:
Loan Amount (P): $300,000
Annual Interest Rate: 5%
Loan Term: 30 years
First, we convert the annual rate to a monthly rate and the loan term to months:
Number of Payments (n): 30 years * 12 months/year = 360 months
Now, we plug these values into the formula:
M = 300,000 [ 0.00416667(1 + 0.00416667)^360 ] / [ (1 + 0.00416667)^360 – 1]
M = 300,000 [ 0.00416667 * (1.00416667)^360 ] / [ (1.00416667)^360 – 1]
M = 300,000 [ 0.00416667 * 4.467744 ] / [ 4.467744 – 1]
M = 300,000 [ 0.0186156 ] / [ 3.467744 ]
M = 5584.68 / 3.467744
M ≈ $1,609.65
So, the estimated principal and interest payment would be approximately $1,609.65 per month.
Over the life of the loan, the total amount paid would be: $1,609.65 * 360 = $579,474.00. The total interest paid would be $579,474.00 – $300,000 = $279,474.00.
Important Considerations
Escrow: Your actual monthly housing payment will likely be higher due to property taxes, homeowner's insurance, and potentially HOA fees or PMI. These are often collected by the lender in an escrow account and paid on your behalf.
Interest Rates: Mortgage rates fluctuate daily. The rate you secure will significantly impact your monthly payment and total interest paid.
Loan Types: This calculator is for a fixed-rate mortgage. Adjustable-rate mortgages (ARMs) have interest rates that can change over time, affecting your payment.
Fees: Loan origination fees, appraisal fees, and other closing costs are not included in this monthly payment calculation.
Use this calculator as a starting point to understand the basic cost of borrowing. Always consult with a mortgage professional for personalized advice and accurate quotes.
function calculateMortgage() {
var loanAmount = parseFloat(document.getElementById("loanAmount").value);
var annualInterestRate = parseFloat(document.getElementById("annualInterestRate").value);
var loanTermYears = parseInt(document.getElementById("loanTermYears").value);
var monthlyPaymentResult = document.getElementById("monthlyPayment");
var totalPaymentResult = document.getElementById("totalPayment");
var totalInterestResult = document.getElementById("totalInterest");
// Clear previous results if inputs are invalid
monthlyPaymentResult.innerText = "$0.00";
totalPaymentResult.innerText = "Total Paid: $0.00";
totalInterestResult.innerText = "Total Interest: $0.00";
// Input validation
if (isNaN(loanAmount) || loanAmount <= 0) {
alert("Please enter a valid Loan Amount.");
return;
}
if (isNaN(annualInterestRate) || annualInterestRate < 0) {
alert("Please enter a valid Annual Interest Rate.");
return;
}
if (isNaN(loanTermYears) || loanTermYears <= 0) {
alert("Please enter a valid Loan Term in years.");
return;
}
// Calculate monthly interest rate
var monthlyInterestRate = annualInterestRate / 100 / 12;
// Calculate total number of payments
var numberOfPayments = loanTermYears * 12;
var monthlyPayment;
// Handle the case where interest rate is 0
if (monthlyInterestRate === 0) {
monthlyPayment = loanAmount / numberOfPayments;
} else {
// Calculate monthly payment using the mortgage formula
var numerator = loanAmount * monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments);
var denominator = Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1;
monthlyPayment = numerator / denominator;
}
// Format the results
var formattedMonthlyPayment = monthlyPayment.toFixed(2);
var formattedTotalPayment = (monthlyPayment * numberOfPayments).toFixed(2);
var formattedTotalInterest = ((monthlyPayment * numberOfPayments) – loanAmount).toFixed(2);
// Display the results
monthlyPaymentResult.innerText = "$" + formattedMonthlyPayment;
totalPaymentResult.innerText = "Total Paid: $" + formattedTotalPayment;
totalInterestResult.innerText = "Total Interest: $" + formattedTotalInterest;
}