Use this comprehensive mortgage calculator to estimate your monthly house payments. Simply enter the home price, your down payment, interest rate, and loan term to see exactly how much you will pay each month, including estimates for property taxes and insurance.
Total Monthly Payment
$0.00
Includes Principal, Interest, Taxes & Insurance
Principal & Interest
$0.00
Loan Amount
$0.00
Total Interest Paid
$0.00
Payoff Date
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How Mortgage Payments Are Calculated
Understanding the formula behind your mortgage payments can help you make better financial decisions. A standard mortgage payment typically consists of four main components, often referred to as PITI:
Principal: The portion of your payment that goes toward paying down the loan balance.
Interest: The cost of borrowing the money, paid to the lender.
Taxes: Real estate property taxes assessed by your local government.
Insurance: Homeowners insurance to protect the property against damage.
The Amortization Formula
The core calculation for the Principal and Interest (P&I) portion uses the standard amortization formula:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
Where:
M = Total monthly payment
P = The principal loan amount (Home Price minus Down Payment)
i = Monthly interest rate (Annual Rate divided by 12)
n = Number of payments (Loan Term in years multiplied by 12)
Factors Affecting Your Mortgage Rate
While the calculator gives you a mathematical estimate, your actual payments will depend on the interest rate you secure. Several factors influence this rate:
Credit Score: Higher scores generally qualify for lower interest rates.
Down Payment: A larger down payment (20% or more) can reduce your rate and eliminate the need for Private Mortgage Insurance (PMI).
Loan Term: 15-year loans typically have lower interest rates than 30-year loans, though monthly payments are higher.
Economic Conditions: Inflation and Federal Reserve policies impact market rates daily.
Why Include Taxes and Insurance?
Many first-time homebuyers focus solely on the principal and interest payment. However, most lenders require an escrow account where they collect 1/12th of your annual property tax and insurance premiums each month. Ignoring these costs can lead to underestimating your monthly budget by hundreds of dollars.
Tips for Lowering Your Monthly Payment
If the calculated payment is higher than your budget allows, consider these strategies:
Increase your down payment: This reduces the principal loan amount.
Shop for cheaper insurance: Compare quotes from different providers.
Buy "points": Pay an upfront fee to lower your interest rate for the life of the loan.
Extend the term: While you pay more interest overall, a 30-year term has lower monthly payments than a 15-year term.
function calculateMortgage() {
// 1. Get Input Values
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);
var annualTax = parseFloat(document.getElementById("propertyTax").value);
var annualInsurance = parseFloat(document.getElementById("homeInsurance").value);
// 2. Validate Inputs
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(annualRate) || isNaN(years)) {
// If critical numbers are missing, do not attempt calculation yet
return;
}
// Handle optional fields for tax/insurance if empty
if (isNaN(annualTax)) annualTax = 0;
if (isNaN(annualInsurance)) annualInsurance = 0;
// 3. Perform Calculations
var principal = homePrice – downPayment;
// Monthly Interest Rate (r) and Total Payments (n)
var r = (annualRate / 100) / 12;
var n = years * 12;
var monthlyPI = 0;
if (r === 0) {
monthlyPI = principal / n;
} else {
// M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
monthlyPI = principal * ( (r * Math.pow(1 + r, n)) / (Math.pow(1 + r, n) – 1) );
}
var monthlyTax = annualTax / 12;
var monthlyInsurance = annualInsurance / 12;
var totalMonthly = monthlyPI + monthlyTax + monthlyInsurance;
var totalCostOfLoan = (monthlyPI * n);
var totalInterest = totalCostOfLoan – principal;
// Calculate Payoff Date
var today = new Date();
var payoffDateObj = new Date(today.setMonth(today.getMonth() + n));
var options = { year: 'numeric', month: 'long' };
var payoffDateString = payoffDateObj.toLocaleDateString("en-US", options);
// 4. Update UI
// Ensure inputs are not negative for display logic (basic sanity check)
if (principal < 0) {
principal = 0;
totalMonthly = 0;
totalInterest = 0;
}
document.getElementById("mpcResults").style.display = "block";
document.getElementById("totalMonthlyPayment").innerHTML = "$" + totalMonthly.toLocaleString("en-US", {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("principalInterest").innerHTML = "$" + monthlyPI.toLocaleString("en-US", {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("totalLoanAmount").innerHTML = "$" + principal.toLocaleString("en-US", {minimumFractionDigits: 0, maximumFractionDigits: 0});
document.getElementById("totalInterestPaid").innerHTML = "$" + totalInterest.toLocaleString("en-US", {minimumFractionDigits: 0, maximumFractionDigits: 0});
document.getElementById("payoffDate").innerHTML = payoffDateString;
}
// Run once on load to populate with default values
window.onload = function() {
calculateMortgage();
};