Your Estimated Monthly Payment (Principal & Interest)
$0.00
Note: This estimate does not include property taxes, homeowner's insurance, or PMI.
Understanding Your Rocket Mortgage Payment
When considering a mortgage, understanding how your monthly payment is calculated is crucial. Rocket Mortgage, like other lenders, bases your primary monthly payment on the loan amount, interest rate, and the term of the loan. This calculator provides an estimate for the principal and interest (P&I) portion of your payment, which is a core component of your total housing expense.
The Mortgage Payment Formula:
The standard formula used to calculate a fixed-rate mortgage payment is:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
Where:
M = Your total monthly mortgage payment (principal and 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)
How the Calculator Works:
1. Home Price & Down Payment: You enter the total price of the home you're interested in and the percentage you plan to pay as a down payment. The calculator then determines the Principal Loan Amount (P) by subtracting your down payment from the home price.
2. Loan Term: You select the duration of your mortgage (e.g., 15, 20, 30 years). This determines the total number of payments (n).
3. Interest Rate: You input the annual interest rate you expect to receive. The calculator converts this into a monthly interest rate (i) by dividing by 12.
4. Calculation: The formula above is applied using these values to compute your estimated monthly principal and interest payment (M).
Important Considerations:
This calculator provides an estimate for Principal and Interest (P&I) only. Your actual total monthly mortgage payment will likely be higher because it typically includes other costs:
Property Taxes: Annual taxes are usually divided by 12 and added to your monthly payment, often collected in an escrow account.
Homeowner's Insurance: The cost of insuring your home against damage, also typically paid monthly via escrow.
Private Mortgage Insurance (PMI): If your down payment is less than 20%, lenders usually require PMI to protect themselves against borrower default. This cost is added to your monthly payment.
For a precise quote, always consult directly with a mortgage lender like Rocket Mortgage. They can provide personalized details based on your full financial profile and current market conditions.
function calculateMortgage() {
var homePrice = parseFloat(document.getElementById("homePrice").value);
var downPaymentPercent = parseFloat(document.getElementById("downPayment").value);
var loanTermYears = parseInt(document.getElementById("loanTerm").value);
var annualInterestRate = parseFloat(document.getElementById("interestRate").value);
// Input validation
if (isNaN(homePrice) || homePrice <= 0) {
alert("Please enter a valid Home Price.");
return;
}
if (isNaN(downPaymentPercent) || downPaymentPercent 100) {
alert("Please enter a valid Down Payment percentage between 0 and 100.");
return;
}
if (isNaN(loanTermYears) || loanTermYears <= 0) {
alert("Please enter a valid Loan Term in years.");
return;
}
if (isNaN(annualInterestRate) || annualInterestRate <= 0) {
alert("Please enter a valid Annual Interest Rate.");
return;
}
var loanAmount = homePrice * (1 – (downPaymentPercent / 100));
var monthlyInterestRate = annualInterestRate / 100 / 12;
var numberOfPayments = loanTermYears * 12;
var monthlyPayment = 0;
// Handle cases where interest rate is very low or zero to avoid division by zero or extremely large numbers
if (monthlyInterestRate === 0) {
monthlyPayment = loanAmount / numberOfPayments;
} else {
monthlyPayment = loanAmount * (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments)) / (Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1);
}
// Display the result
var formattedMonthlyPayment = monthlyPayment.toFixed(2);
document.getElementById("result-monthly-payment").innerText = "$" + formattedMonthlyPayment;
}
// Update slider value display
var downPaymentSlider = document.getElementById("downPayment");
var downPaymentValueDisplay = document.getElementById("downPaymentValue");
downPaymentSlider.oninput = function() {
var value = this.value;
downPaymentValueDisplay.innerText = value + "%";
// Recalculate if values change, can be removed if only manual button click is desired
// calculateMortgage();
}
// Initial call to set default values if needed, or to ensure calculation on load
// calculateMortgage();