Your estimated monthly principal & interest payment: $0.00
Understanding Your Mortgage Payment
This calculator helps you estimate your monthly principal and interest (P&I) payment for a mortgage loan. It's a crucial tool for understanding affordability and comparing loan offers. New American Funding, like other lenders, uses a standard formula to calculate these payments.
The Formula Explained
The monthly mortgage payment (M) is calculated using the following formula:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
Where:
P = Principal loan amount (the total amount you borrow).
i = Monthly interest rate (annual rate divided by 12, expressed as a decimal).
n = Total number of payments over the loan's lifetime (loan term in years multiplied by 12).
How the Calculator Works:
Loan Amount (P): Enter the total amount you intend to borrow for your home.
Annual Interest Rate (%): Input the yearly interest rate offered by the lender. This is converted to a monthly rate (divided by 12) and then to a decimal for the calculation.
Loan Term (Years): Specify the duration of your loan in years. This is converted to the total number of monthly payments.
The calculator then applies the formula to provide an estimated monthly P&I payment. This figure does not include other potential housing costs like property taxes, homeowners insurance, or Private Mortgage Insurance (PMI), which are often bundled into your total monthly housing expense (escrow).
Why Use This Calculator?
Budgeting: Get a clear idea of how much your mortgage might cost each month to ensure it fits your budget.
Loan Comparison: Easily compare different loan scenarios with varying interest rates and terms.
Affordability Check: Determine how much home you can realistically afford based on your desired monthly payment.
This tool is for estimation purposes only. Actual loan terms and payments may vary. It's always recommended to speak with a New American Funding loan specialist for personalized advice and precise figures.
function updateInterestRate(value) {
document.getElementById('interestRate').value = value;
calculateMortgage();
}
function updateLoanTerm(value) {
document.getElementById('loanTerm').value = value;
calculateMortgage();
}
function calculateMortgage() {
var loanAmountInput = document.getElementById('loanAmount');
var interestRateInput = document.getElementById('interestRate');
var loanTermInput = document.getElementById('loanTerm');
var monthlyPaymentDisplay = document.getElementById('monthlyPayment');
var loanAmount = parseFloat(loanAmountInput.value);
var annualInterestRate = parseFloat(interestRateInput.value);
var loanTermYears = parseFloat(loanTermInput.value);
// Clear previous error messages or results
monthlyPaymentDisplay.textContent = "Calculating…";
// Input validation
if (isNaN(loanAmount) || loanAmount <= 0) {
monthlyPaymentDisplay.textContent = "Please enter a valid loan amount.";
return;
}
if (isNaN(annualInterestRate) || annualInterestRate < 0) {
monthlyPaymentDisplay.textContent = "Please enter a valid annual interest rate.";
return;
}
if (isNaN(loanTermYears) || loanTermYears 0) {
var powRate = Math.pow(1 + monthlyInterestRate, numberOfPayments);
monthlyPayment = loanAmount * (monthlyInterestRate * powRate) / (powRate – 1);
} else {
// Handle the case of 0% interest rate
monthlyPayment = loanAmount / numberOfPayments;
}
// Format the monthly payment to two decimal places
var formattedMonthlyPayment = monthlyPayment.toFixed(2);
// Display the result
monthlyPaymentDisplay.textContent = "$" + formattedMonthlyPayment;
}
// Initial calculation on page load if inputs have default values
document.addEventListener('DOMContentLoaded', function() {
// Optionally set default values if you want them
// document.getElementById('loanAmount').value = 300000;
// document.getElementById('interestRate').value = 4.5;
// document.getElementById('loanTerm').value = 30;
// document.getElementById('interestRateSlider').value = 4.5;
// document.getElementById('loanTermSlider').value = 30;
calculateMortgage();
});