Comprehensive Mortgage Payment Calculator
Use this specific calculator to determine your estimated monthly mortgage payment, including principal, interest, property taxes, and homeowner’s insurance. Understanding the breakdown of your monthly housing costs is crucial for smart financial planning when buying a home.
30 Years
20 Years
15 Years
10 Years
Estimated Monthly Payment:
Loan Amount:
Total Interest Paid (Over Life of Loan):
Total Cost of Loan (Principal + Interest):
* Note: This calculation does not include Private Mortgage Insurance (PMI), HOA fees, or other specific closing costs.
function calculateMortgage() {
// 1. Get inputs
var homePrice = parseFloat(document.getElementById(“homePrice”).value);
var downPayment = parseFloat(document.getElementById(“downPayment”).value);
var loanTermYears = parseInt(document.getElementById(“loanTerm”).value);
var interestRateAnnual = parseFloat(document.getElementById(“interestRate”).value);
var propertyTaxAnnual = parseFloat(document.getElementById(“propertyTaxAnnual”).value);
var homeInsuranceAnnual = parseFloat(document.getElementById(“homeInsuranceAnnual”).value);
// 2. Validate inputs & handle NaN
if (isNaN(homePrice) || homePrice <= 0) homePrice = 0;
if (isNaN(downPayment) || downPayment < 0) downPayment = 0;
if (isNaN(loanTermYears)) loanTermYears = 30;
if (isNaN(interestRateAnnual) || interestRateAnnual < 0) interestRateAnnual = 0;
if (isNaN(propertyTaxAnnual) || propertyTaxAnnual < 0) propertyTaxAnnual = 0;
if (isNaN(homeInsuranceAnnual) || homeInsuranceAnnual < 0) homeInsuranceAnnual = 0;
// 3. Basic Calculations
var loanAmount = homePrice – downPayment;
if (loanAmount <= 0) {
alert("Down payment cannot be equal to or greater than the home price.");
document.getElementById("calcResults").style.display = "none";
return;
}
var numPayments = loanTermYears * 12;
var monthlyTax = propertyTaxAnnual / 12;
var monthlyInsurance = homeInsuranceAnnual / 12;
var monthlyPI = 0;
// 4. Mortgage Formula Logic
if (interestRateAnnual === 0) {
// Handle 0% interest edge case
monthlyPI = loanAmount / numPayments;
} else {
var monthlyRate = (interestRateAnnual / 100) / 12;
// M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var mathPower = Math.pow(1 + monthlyRate, numPayments);
monthlyPI = loanAmount * ( (monthlyRate * mathPower) / (mathPower – 1) );
}
var totalMonthly = monthlyPI + monthlyTax + monthlyInsurance;
var totalCost = monthlyPI * numPayments;
var totalInterest = totalCost – loanAmount;
// 5. Format & Display Results
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
document.getElementById("totalMonthlyPayment").innerHTML = formatter.format(totalMonthly);
document.getElementById("resultPI").innerHTML = formatter.format(monthlyPI);
document.getElementById("resultTax").innerHTML = formatter.format(monthlyTax);
document.getElementById("resultInsurance").innerHTML = formatter.format(monthlyInsurance);
document.getElementById("resultLoanAmount").innerHTML = formatter.format(loanAmount);
document.getElementById("totalInterestPaid").innerHTML = formatter.format(totalInterest);
document.getElementById("totalCostOfLoan").innerHTML = formatter.format(totalCost);
document.getElementById("calcResults").style.display = "block";
}
Understanding Your Mortgage Payment Components
When you take out a mortgage to buy a home, your monthly payment typically consists of four distinct parts, often abbreviated as PITI: Principal, Interest, Taxes, and Insurance. Our calculator breaks these down so you can see exactly where your money is going.
1. Principal and Interest (P&I)
This is the core component of your loan repayment. The **principal** is the money going toward paying off the original loan balance. The **interest** is the cost of borrowing that money from the lender. In the early years of a standard amortization schedule, the majority of your P&I payment goes toward interest, while in later years, more goes toward reducing the principal balance.
2. Property Taxes and Insurance (Escrow)
Most lenders require an escrow account. They collect a portion of your estimated annual property taxes and homeowner’s insurance premiums each month along with your P&I payment. They hold these funds and pay the tax and insurance bills on your behalf when they come due. This ensures the property is secured against tax liens and uninsured damage.
- Property Taxes: Assessed by your local government based on the property’s value.
- Homeowner’s Insurance: Protects your home against damages like fire, theft, or storms. Lenders require this to protect their collateral.
How Factors Affect Your Monthly Payment
Small changes in your loan inputs can have significant impacts on your monthly obligation and the total cost of the home.
- Interest Rate: Even a 1% difference in interest rate can change your monthly payment by hundreds of dollars and your total interest paid over 30 years by tens of thousands.
- Loan Term: A 15-year term will have much higher monthly payments than a 30-year term, but you will pay significantly less in total interest because you are borrowing the money for half the time.
- Down Payment: A larger down payment reduces the loan amount, lowering your monthly P&I. If you put down less than 20%, you will likely also have to pay Private Mortgage Insurance (PMI), which is an extra monthly cost not included in this specific calculator.
Real-World Example Calculation
Let’s look at a realistic scenario using the calculator above. Suppose you are buying a home and have the following figures:
- Home Price: $425,000
- Down Payment: $85,000 (20%)
- Loan Amount: $340,000
- Interest Rate: 7.0%
- Loan Term: 30 Years
- Annual Property Tax: $4,200 ($350/month)
- Annual Insurance: $1,500 ($125/month)
Based on standard amortization formulas, the Principal & Interest portion would be approximately $2,262.10. When you add the monthly tax ($350) and insurance ($125), the total estimated monthly payment becomes $2,737.10. Over the 30-year life of this loan, you would pay approximately $474,357 just in interest.