Estimate your monthly house payments based on price, down payment, and rates.
Estimated Monthly Payment
$0.00
How to Calculate Your Monthly Mortgage Payment
Buying a home is one of the most significant financial decisions you will ever make. Understanding how your monthly payment is structured is vital for long-term budgeting. This mortgage calculator uses the standard amortization formula to help you determine your "Principal and Interest" (P&I) costs.
The Mortgage Formula
The mathematical formula used to calculate a fixed-rate mortgage payment is:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
M: Total monthly payment
P: Principal loan amount (Home price minus down payment)
i: Monthly interest rate (Annual rate divided by 12)
n: Number of months (Years multiplied by 12)
Factors That Influence Your Payment
While our calculator focuses on the loan itself, your total "PITI" (Principal, Interest, Taxes, and Insurance) may also include:
Component
Description
Principal
The actual balance of the loan being paid back.
Interest
The cost of borrowing money from the lender.
Property Taxes
Annual taxes charged by your local government.
Homeowners Insurance
Protection against damage to your property.
PMI
Private Mortgage Insurance (usually required if down payment is under 20%).
Example Calculation
If you purchase a $400,000 home with a $80,000 down payment (20%) at a 6.5% interest rate for 30 years:
Loan Amount: $320,000
Monthly Interest: 0.005416 (6.5% / 12)
Total Months: 360
Resulting Payment: ~$2,022.62 per month
Tips for Lowering Your Monthly Mortgage
To reduce your monthly financial burden, consider these strategies:
Larger Down Payment: Every dollar paid upfront reduces the principal balance and the interest charged over time.
Improve Credit Score: Higher credit scores typically qualify for lower interest rates.
Shorten the Term: While a 15-year mortgage has higher monthly payments, you will pay significantly less in total interest.
Refinance: If market rates drop after your purchase, refinancing can lower your monthly commitment.
function calculateMortgage() {
var homePrice = parseFloat(document.getElementById('homePrice').value);
var downPayment = parseFloat(document.getElementById('downPayment').value);
var annualInterest = parseFloat(document.getElementById('interestRate').value);
var years = parseFloat(document.getElementById('loanTerm').value);
var resultDiv = document.getElementById('mortgageResult');
var paymentDisplay = document.getElementById('monthlyPaymentDisplay');
var breakdownDisplay = document.getElementById('mortgageBreakdown');
// Validation
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(annualInterest) || isNaN(years)) {
alert("Please enter valid numeric values in all fields.");
return;
}
if (downPayment >= homePrice) {
alert("Down payment cannot be equal to or greater than the home price.");
return;
}
var principal = homePrice – downPayment;
var monthlyInterest = (annualInterest / 100) / 12;
var numberOfPayments = years * 12;
var monthlyPayment;
if (monthlyInterest === 0) {
monthlyPayment = principal / numberOfPayments;
} else {
var x = Math.pow(1 + monthlyInterest, numberOfPayments);
monthlyPayment = (principal * x * monthlyInterest) / (x – 1);
}
var totalRepayment = monthlyPayment * numberOfPayments;
var totalInterest = totalRepayment – principal;
// Display Results
resultDiv.style.display = 'block';
paymentDisplay.innerText = '$' + monthlyPayment.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
breakdownDisplay.innerHTML =
"Loan Principal: $" + principal.toLocaleString() + "" +
"Total Interest Paid: $" + totalInterest.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}) + "" +
"Total of " + numberOfPayments + " Payments: $" + totalRepayment.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
// Smooth scroll to result
resultDiv.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}