Calculate your estimated monthly mortgage payment based on loan details.
Your Estimated Monthly Payment: $0.00
Understanding Your Mortgage Payment
A mortgage is a loan used to purchase real estate. The monthly mortgage payment is a crucial figure for any prospective homeowner, as it represents a significant ongoing financial commitment. This calculator helps you estimate that payment.
The calculation for a fixed-rate mortgage's monthly principal and interest payment is based on the following formula:
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. This is calculated by dividing your annual interest rate by 12. For example, if your annual rate is 6%, your monthly rate is 0.06 / 12 = 0.005.
n = The total number of payments over the loan's lifetime. This is calculated by multiplying your loan term in years by 12. For a 30-year mortgage, this would be 30 * 12 = 360 payments.
How the Calculator Works:
1. Loan Amount (P): You input the total amount you plan to borrow for the home.
2. Annual Interest Rate: You provide the yearly interest rate offered by the lender. The calculator converts this into a monthly rate (i).
3. Loan Term (Years): You specify the duration of the loan in years. The calculator converts this into the total number of monthly payments (n).
The calculator then plugs these values into the mortgage payment formula to derive your estimated monthly principal and interest payment.
Important Considerations:
This calculator provides an estimate for the Principal and Interest (P&I) portion of your monthly mortgage payment. It does not include other costs such as:
Property Taxes
Homeowner's Insurance
Private Mortgage Insurance (PMI) if your down payment is less than 20%
Homeowner Association (HOA) Dues
These additional costs are often included in an Escrow Account and are paid to your lender, who then disburses them to the relevant authorities. Your Total Monthly Housing Payment will be higher than the P&I calculated here.
Use this tool to compare different loan scenarios, understand affordability, and better prepare for the financial commitment of homeownership.
function calculateMortgagePayment() {
var principal = parseFloat(document.getElementById("loanAmount").value);
var annualRate = parseFloat(document.getElementById("annualInterestRate").value);
var years = parseFloat(document.getElementById("loanTermYears").value);
var resultDiv = document.getElementById("result");
if (isNaN(principal) || principal <= 0 ||
isNaN(annualRate) || annualRate <= 0 ||
isNaN(years) || years <= 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
var monthlyRate = annualRate / 100 / 12;
var numberOfPayments = years * 12;
// Calculate monthly payment using the mortgage formula
// M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
var numerator = monthlyRate * Math.pow(1 + monthlyRate, numberOfPayments);
var denominator = Math.pow(1 + monthlyRate, numberOfPayments) – 1;
if (denominator === 0) {
resultDiv.innerHTML = "Calculation error. Please check inputs.";
return;
}
var monthlyPayment = principal * (numerator / denominator);
resultDiv.innerHTML = "Your Estimated Monthly Payment: $" + monthlyPayment.toFixed(2) + "";
}