Calculate your estimated monthly mortgage payment.
Estimated Monthly Payment:
$0.00
Understanding Your Mortgage Payment
A mortgage is a loan used to purchase real estate, typically a home. The monthly payment for a mortgage usually includes several components, but for a simple calculator, we focus on the principal and interest (P&I). This calculator estimates the fixed monthly P&I payment based on the loan amount, interest rate, and loan term.
The Math Behind the Calculation
The standard formula for calculating a fixed monthly mortgage payment (M) is as follows:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
Where:
P = Principal loan amount (the total amount borrowed)
i = Monthly interest rate (Annual interest rate divided by 12)
n = Total number of payments (Loan term in years multiplied by 12)
Example Calculation
Let's consider a mortgage with the following details:
Loan Amount (P): $250,000
Annual Interest Rate: 4.5%
Loan Term: 30 Years
First, we need to convert the annual interest rate to a monthly interest rate (i) and the loan term to the total number of payments (n):
Therefore, the estimated monthly principal and interest payment for this mortgage would be approximately $1,265.90.
Important Considerations
This simple calculator provides an estimate for the principal and interest portion of your mortgage payment. Your actual total monthly housing expense will likely be higher and may include:
Property Taxes: Annual taxes divided by 12.
Homeowner's Insurance: Annual premiums divided by 12.
Private Mortgage Insurance (PMI): If your down payment is less than 20%.
Homeowner Association (HOA) Fees: If applicable.
It's crucial to consult with a mortgage lender or financial advisor for a precise quote and to understand all associated costs and terms of your specific mortgage.
function calculateMortgage() {
var loanAmountInput = document.getElementById("loanAmount");
var annualInterestRateInput = document.getElementById("annualInterestRate");
var loanTermInput = document.getElementById("loanTerm");
var resultValueElement = document.getElementById("result-value");
var loanAmount = parseFloat(loanAmountInput.value);
var annualInterestRate = parseFloat(annualInterestRateInput.value);
var loanTerm = parseFloat(loanTermInput.value);
if (isNaN(loanAmount) || isNaN(annualInterestRate) || isNaN(loanTerm) ||
loanAmount <= 0 || annualInterestRate < 0 || loanTerm <= 0) {
resultValueElement.textContent = "Invalid input. Please enter positive numbers.";
return;
}
var monthlyInterestRate = annualInterestRate / 100 / 12;
var numberOfPayments = loanTerm * 12;
var monthlyPayment;
if (monthlyInterestRate === 0) {
monthlyPayment = loanAmount / numberOfPayments;
} else {
monthlyPayment = loanAmount * (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments)) / (Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1);
}
if (isNaN(monthlyPayment) || !isFinite(monthlyPayment)) {
resultValueElement.textContent = "Calculation error. Please check inputs.";
return;
}
resultValueElement.textContent = "$" + monthlyPayment.toFixed(2);
}