Estimate your potential monthly mortgage payment based on loan details.
Estimated Monthly Payment (Principal & 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 helps you estimate the principal and interest portion of your monthly mortgage payment, allowing you to better budget and compare loan offers.
The Math Behind the Calculation
The calculation for a standard fixed-rate mortgage payment uses the following formula:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
M = Your total monthly mortgage payment (principal and interest)
P = The principal loan amount (the amount you borrow)
i = Your monthly interest rate (annual rate divided by 12)
n = The total number of payments over the loan's lifetime (loan term in years multiplied by 12)
Example: If you borrow $200,000 (P) at an annual interest rate of 3.5% (which is 0.035/12 = 0.00291667 monthly, or 'i') for 30 years (which is 30 * 12 = 360 payments, or 'n'), your estimated monthly principal and interest payment would be approximately $898.09.
Factors Not Included
It's important to note that this calculator provides an estimate for principal and interest (P&I) only. Your actual total monthly housing payment (often called PITI) will likely be higher and typically includes:
Property Taxes: Paid to your local government.
Homeowners Insurance: Required by lenders to protect against damage.
Private Mortgage Insurance (PMI): If your down payment is less than 20% of the home's value.
HOA Dues: If applicable, for homeowners associations.
How to Use This Calculator
1. Loan Amount: Enter the total amount you plan to borrow for the home purchase.
2. Annual Interest Rate: Input the annual interest rate you've been quoted or are targeting. Remember that actual rates depend on your creditworthiness, market conditions, and the loan type.
3. Loan Term (Years): Select the duration of your mortgage, commonly 15 or 30 years.
4. Calculate: Click the "Calculate Monthly Payment" button.
The result will show your estimated monthly principal and interest payment. Use this to gauge affordability and discuss options with your mortgage lender.
function calculateMortgage() {
var loanAmount = parseFloat(document.getElementById("loanAmount").value);
var annualInterestRate = parseFloat(document.getElementById("annualInterestRate").value);
var loanTermYears = parseInt(document.getElementById("loanTermYears").value);
var resultElement = document.getElementById("monthlyPayment");
if (isNaN(loanAmount) || isNaN(annualInterestRate) || isNaN(loanTermYears) || loanAmount <= 0 || annualInterestRate < 0 || loanTermYears 0) {
// Standard Amortization Formula
monthlyPayment = loanAmount * (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments)) / (Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1);
} else {
// If interest rate is 0, payment is just principal divided by number of payments
monthlyPayment = loanAmount / numberOfPayments;
}
resultElement.textContent = "$" + monthlyPayment.toFixed(2);
resultElement.style.color = "#28a745"; // Success green
}