Calculate your monthly payments and total interest costs instantly.
Estimated Monthly Payment$0.00
Total Principal$0.00
Total Interest$0.00
Understanding Your Mortgage Repayments
Buying a home is often the largest financial commitment of your life. Using a Mortgage Repayment Calculator helps you understand the long-term implications of your loan beyond just the sticker price of the property.
How the Mortgage Calculation Works
Our calculator uses the standard fixed-rate mortgage formula to determine your monthly payment of principal and interest. The formula is:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
M: Total monthly payment.
P: Principal loan amount (Home Price – Down Payment).
i: Monthly interest rate (Annual Rate divided by 12 months).
n: Total number of monthly payments (Years multiplied by 12).
Example Calculation
Let's say you purchase a home for $450,000 with a $90,000 down payment (20%). You secure a 30-year fixed rate at 7% interest.
Loan Principal: $360,000
Monthly Payment: $2,395.09
Total Interest Paid: $502,232.40
Notice that over 30 years, you actually pay more in interest than the original loan amount. This is why even a 0.5% difference in interest rates can save you tens of thousands of dollars over the life of the loan.
Factors That Impact Your Payment
While this calculator provides the core Principal and Interest (P&I) payment, remember that your actual monthly "PITI" payment (Principal, Interest, Taxes, and Insurance) may also include:
Property Taxes: Usually calculated annually and divided by 12.
Homeowners Insurance: Required by lenders to protect the asset.
Private Mortgage Insurance (PMI): Typically required if your down payment is less than 20%.
HOA Fees: Monthly dues for managed communities or condos.
function calculateMortgage() {
var homePrice = parseFloat(document.getElementById("loanAmount").value);
var downPayment = parseFloat(document.getElementById("downPayment").value) || 0;
var annualRate = parseFloat(document.getElementById("interestRate").value);
var loanTermYears = parseFloat(document.getElementById("loanTerm").value);
var resultDiv = document.getElementById("mortgage-results");
if (isNaN(homePrice) || isNaN(annualRate) || isNaN(loanTermYears) || homePrice <= 0) {
alert("Please enter valid positive numbers for price, rate, and term.");
return;
}
var principal = homePrice – downPayment;
if (principal <= 0) {
alert("Down payment cannot be greater than or equal to the home price.");
return;
}
var monthlyRate = (annualRate / 100) / 12;
var totalMonths = loanTermYears * 12;
var monthlyPayment;
// Handle 0% interest case
if (monthlyRate === 0) {
monthlyPayment = principal / totalMonths;
} else {
var x = Math.pow(1 + monthlyRate, totalMonths);
monthlyPayment = (principal * x * monthlyRate) / (x – 1);
}
var totalCost = monthlyPayment * totalMonths;
var totalInterest = totalCost – principal;
document.getElementById("monthlyPaymentOutput").innerHTML = "$" + monthlyPayment.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("totalPrincipalOutput").innerHTML = "$" + principal.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("totalInterestOutput").innerHTML = "$" + totalInterest.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
resultDiv.style.display = "block";
resultDiv.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}