Estimate your monthly housing costs including tax and insurance.
Principal & Interest:$0.00
Property Tax (Monthly):$0.00
Home Insurance (Monthly):$0.00
Total Monthly Payment:$0.00
Total Interest Paid Over Loan:$0.00
Understanding Your Mortgage Calculation
Using a reliable Mortgage Payment Calculator is an essential step in the home buying process. It helps you determine exactly how much house you can afford by breaking down the total monthly costs involved in owning a property. While many buyers focus solely on the principal and interest, true affordability calculation must include escrow items like property taxes and insurance.
The Components of Your Monthly Payment (PITI)
In the real estate industry, your monthly mortgage payment is often referred to as PITI. Here is how our calculator breaks it down:
Principal: The portion of your payment that goes toward paying down the loan balance (the Home Price minus your Down Payment).
Interest: The cost of borrowing money from your lender, calculated based on your Annual Percentage Rate (APR).
Taxes: Property taxes assessed by your local government, typically paid annually but collected monthly by lenders into an escrow account.
Insurance: Homeowners insurance to protect your property against damage, also typically collected monthly.
Example Calculation
Let's look at a realistic example. If you purchase a home for $350,000 and make a 20% down payment ($70,000), you are financing $280,000.
With a 30-year fixed loan at an interest rate of 6.5%:
Your monthly Principal & Interest would be approximately $1,769.
If your annual property taxes are $3,500, that adds roughly $292/month.
If your insurance is $1,200 annually, that adds another $100/month.
Your total estimated monthly payment would be roughly $2,161. This comprehensive view ensures you aren't surprised by the "hidden" costs of homeownership.
How Interest Rates Impact Your Payment
Even a small change in interest rates can significantly affect your monthly cash flow. On a $300,000 loan, the difference between a 6% and a 7% interest rate is roughly $200 per month. Over the life of a 30-year loan, that 1% difference costs you approximately $72,000 in additional interest payments. Use the calculator above to scenario-test different rates to see how they impact your budget.
function calculateMortgage() {
// 1. Get Input Values
var homePrice = parseFloat(document.getElementById('homePrice').value);
var downPayment = parseFloat(document.getElementById('downPayment').value);
var interestRate = parseFloat(document.getElementById('interestRate').value);
var years = parseFloat(document.getElementById('loanTerm').value);
var annualTax = parseFloat(document.getElementById('propertyTax').value);
var annualInsurance = parseFloat(document.getElementById('insurance').value);
// 2. Validate Inputs
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) || isNaN(years)) {
alert("Please enter valid numbers for all fields.");
return;
}
// 3. Core Calculations
var loanAmount = homePrice – downPayment;
// Handle case where down payment >= home price
if (loanAmount <= 0) {
document.getElementById('resPrincipalInterest').innerHTML = "$0.00";
document.getElementById('resTax').innerHTML = "$" + (annualTax / 12).toFixed(2);
document.getElementById('resInsurance').innerHTML = "$" + (annualInsurance / 12).toFixed(2);
document.getElementById('resTotal').innerHTML = "$" + ((annualTax + annualInsurance) / 12).toFixed(2);
document.getElementById('resTotalInterest').innerHTML = "$0.00";
document.getElementById('results').style.display = "block";
return;
}
var monthlyRate = (interestRate / 100) / 12;
var numberOfPayments = years * 12;
// Amortization Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var x = Math.pow(1 + monthlyRate, numberOfPayments);
var monthlyPrincipalInterest = (loanAmount * x * monthlyRate) / (x – 1);
// Calculate Monthly Escrow Items
var monthlyTax = annualTax / 12;
var monthlyInsurance = annualInsurance / 12;
// Calculate Totals
var totalMonthlyPayment = monthlyPrincipalInterest + monthlyTax + monthlyInsurance;
var totalCostOfLoan = (monthlyPrincipalInterest * numberOfPayments);
var totalInterestPaid = totalCostOfLoan – loanAmount;
// 4. Update UI with formatted results
// Helper function for currency formatting
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
document.getElementById('resPrincipalInterest').innerHTML = formatter.format(monthlyPrincipalInterest);
document.getElementById('resTax').innerHTML = formatter.format(monthlyTax);
document.getElementById('resInsurance').innerHTML = formatter.format(monthlyInsurance);
document.getElementById('resTotal').innerHTML = formatter.format(totalMonthlyPayment);
document.getElementById('resTotalInterest').innerHTML = formatter.format(totalInterestPaid);
// Show results section
document.getElementById('results').style.display = "block";
}