Estimate your potential monthly mortgage payment for your dream home.
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Estimated Monthly Principal & Interest:
$0.00
Understanding Your Mortgage Payment
Buying a home is a significant financial decision, and understanding your potential mortgage payment is crucial. This calculator helps you estimate the principal and interest portion of your monthly mortgage payment, providing a foundational figure for your home affordability.
How the Calculation Works
The calculation is based on the standard mortgage payment formula, which determines the fixed periodic payment required to fully amortize a loan over a specific period. The formula used is:
$M = P \frac{i(1+i)^n}{(1+i)^n – 1}$
Where:
M = Your total monthly mortgage payment (Principal & Interest)
P = The principal loan amount (Home Price – Down Payment)
i = Your monthly interest rate (Annual Interest Rate / 12 / 100)
n = Total number of payments over the loan's lifetime (Loan Term in Years * 12)
Key Inputs Explained:
Home Price: The total cost of the house you are looking to purchase.
Down Payment Amount: The upfront cash you contribute towards the purchase price. A larger down payment reduces the principal loan amount, typically lowering your monthly payment.
Annual Interest Rate: The yearly interest rate charged by the lender. This is a crucial factor that significantly impacts your monthly payment and the total interest paid over the life of the loan.
Loan Term (Years): The duration over which you agree to repay the loan. Common terms are 15 and 30 years. A shorter term usually results in higher monthly payments but less total interest paid.
What This Calculator Does NOT Include:
It's important to note that this calculator provides an estimate of the Principal & Interest (P&I) portion of your mortgage payment only. Your actual total monthly housing expense will likely be higher and may include:
Property Taxes: Annual taxes assessed by your local government, often paid monthly as part of your mortgage escrow.
Homeowners Insurance: Insurance protecting your home against damage, also typically paid monthly through escrow.
Private Mortgage Insurance (PMI): If your down payment is less than 20% of the home's value, lenders often require PMI, which protects them if you default.
Homeowners Association (HOA) Fees: If applicable, for properties in planned communities.
Lenders like Rocket Mortgage will consider all these factors, along with your creditworthiness, debt-to-income ratio, and employment history, to determine your final loan approval and exact monthly payment. Use this calculator as a starting point to understand your borrowing power and potential monthly obligations.
function calculateMortgage() {
var homePrice = parseFloat(document.getElementById("homePrice").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var loanTerm = parseInt(document.getElementById("loanTerm").value);
var errorMessages = [];
if (isNaN(homePrice) || homePrice <= 0) {
errorMessages.push("Please enter a valid Home Price.");
}
if (isNaN(downPayment) || downPayment homePrice) {
errorMessages.push("Down Payment cannot be greater than the Home Price.");
}
if (isNaN(interestRate) || interestRate 20) {
errorMessages.push("Please enter a valid Annual Interest Rate (e.g., 3.5).");
}
if (isNaN(loanTerm) || loanTerm 50) {
errorMessages.push("Please enter a valid Loan Term in years (e.g., 30).");
}
if (errorMessages.length > 0) {
alert(errorMessages.join("\n"));
document.getElementById("result").textContent = "$0.00";
document.getElementById("resultLabel").textContent = "Estimated Monthly Principal & Interest:";
return;
}
var principal = homePrice – downPayment;
var monthlyInterestRate = interestRate / 100 / 12;
var numberOfPayments = loanTerm * 12;
var monthlyPayment = 0;
if (monthlyInterestRate > 0) {
monthlyPayment = principal * (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments)) / (Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1);
} else { // Handle case for 0% interest rate
monthlyPayment = principal / numberOfPayments;
}
// Format the result to two decimal places
var formattedMonthlyPayment = monthlyPayment.toFixed(2);
document.getElementById("result").textContent = "$" + formattedMonthlyPayment;
document.getElementById("resultLabel").textContent = "Estimated Monthly Principal & Interest:";
}