Estimate your monthly payments and total interest costs.
Estimated Monthly Payment$0.00
Total Loan Amount$0.00
Total Interest Paid$0.00
Total Cost of Loan$0.00
function calculateMortgage() {
var homePrice = parseFloat(document.getElementById('homePrice').value);
var downPayment = parseFloat(document.getElementById('downPayment').value);
var annualRate = parseFloat(document.getElementById('interestRate').value);
var years = parseFloat(document.getElementById('loanTerm').value);
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(annualRate) || isNaN(years) || homePrice <= 0) {
alert("Please enter valid positive numbers for all fields.");
return;
}
var principal = homePrice – downPayment;
if (principal <= 0) {
alert("Down payment cannot be equal to or greater than home price.");
return;
}
var monthlyRate = (annualRate / 100) / 12;
var numberOfPayments = years * 12;
var monthlyPayment = 0;
if (monthlyRate === 0) {
monthlyPayment = principal / numberOfPayments;
} else {
var x = Math.pow(1 + monthlyRate, numberOfPayments);
monthlyPayment = (principal * monthlyRate * x) / (x – 1);
}
var totalCost = monthlyPayment * numberOfPayments;
var totalInterest = totalCost – principal;
document.getElementById('resMonthlyPayment').innerText = "$" + monthlyPayment.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resLoanAmount').innerText = "$" + principal.toLocaleString();
document.getElementById('resTotalInterest').innerText = "$" + totalInterest.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resTotalCost').innerText = "$" + totalCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('results').style.display = 'block';
}
Understanding Your Mortgage Repayments
Buying a home is one of the most significant financial decisions you will ever make. Using a Mortgage Repayment Calculator helps you demystify the numbers, allowing you to see exactly how your home price, down payment, and interest rate interact to determine your monthly budget.
How the Mortgage Payment is Calculated
The standard formula for calculating a fixed-rate mortgage payment is based on an amortization schedule. The formula 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 months).
n: Number of months (Years multiplied by 12).
Key Factors Affecting Your Mortgage
1. Down Payment Size
The more money you put down upfront, the less you need to borrow. A larger down payment reduces your monthly principal and interest payments and may also help you avoid Private Mortgage Insurance (PMI) if you reach the 20% threshold.
2. Interest Rates
Interest rates are determined by the broader economy and your personal credit score. Even a 0.5% difference in your interest rate can result in tens of thousands of dollars in savings over the life of a 30-year loan.
3. Loan Term
While a 30-year loan is the most common, 15-year loans often offer lower interest rates. A shorter term means higher monthly payments but significantly less total interest paid over time.
Example Calculation
Let's look at a realistic scenario for a modern homebuyer:
Home Price: $450,000
Down Payment: $90,000 (20%)
Loan Amount: $360,000
Interest Rate: 7%
Term: 30 Years
In this example, the monthly principal and interest payment would be approximately $2,395.09. Over 30 years, the total interest paid would be $502,232, making the total cost of the loan $862,232.
Tips for Lowering Your Monthly Payment
If the results from the calculator are higher than your budget allows, consider these strategies:
Improve your credit score: A higher score often unlocks lower interest rates.
Save for a bigger down payment: Reducing the principal borrowed is the most direct way to lower payments.
Consider an ARM: Adjustable-Rate Mortgages often have lower initial rates, though they carry more risk long-term.
Buy points: You can pay an upfront fee to "buy down" your interest rate.