Mortgage Payment Calculator
body {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
line-height: 1.6;
color: #333;
max-width: 1200px;
margin: 0 auto;
padding: 20px;
}
.calc-wrapper {
display: flex;
flex-wrap: wrap;
gap: 40px;
margin-bottom: 50px;
background: #f9f9f9;
padding: 30px;
border-radius: 8px;
box-shadow: 0 4px 6px rgba(0,0,0,0.1);
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.calc-inputs {
flex: 1;
min-width: 300px;
}
.calc-results {
flex: 1;
min-width: 300px;
background: #ffffff;
padding: 25px;
border-radius: 8px;
border: 1px solid #e0e0e0;
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.form-group {
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margin-bottom: 8px;
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.input-wrapper {
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.input-suffix {
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.form-control {
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border: 1px solid #ccc;
border-radius: 4px;
box-sizing: border-box;
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.form-control.has-suffix {
padding-right: 35px;
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.btn-calc {
background-color: #0066cc;
color: white;
border: none;
padding: 15px 30px;
font-size: 18px;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
width: 100%;
transition: background-color 0.2s;
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.btn-calc:hover {
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.result-row {
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.result-row:last-child {
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.result-label {
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.result-value {
font-weight: 700;
font-size: 18px;
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.result-main {
text-align: center;
margin-bottom: 25px;
padding-bottom: 25px;
border-bottom: 2px solid #0066cc;
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.result-main .amount {
display: block;
font-size: 42px;
font-weight: 800;
color: #0066cc;
margin-top: 10px;
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.content-section {
max-width: 800px;
margin: 0 auto;
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h2 {
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display: none;
margin-bottom: 15px;
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Mortgage Payment Calculator
Estimated Monthly Payment
$2,245.32
Principal & Interest:
$1,769.49
Property Taxes:
$375.00
Homeowners Insurance:
$100.83
HOA Fees:
$0.00
Total Loan Amount:
$280,000
Total Interest Paid:
$357,016
How Your Mortgage Payment is Calculated
Understanding how your monthly mortgage payment is calculated is a critical step in the home buying process. This calculator breaks down the total cost into its four primary components, often referred to as PITI: Principal, Interest, Taxes, and Insurance.
Principal and Interest (P&I)
This is the core of your loan repayment. Principal is the money that goes towards paying down the actual loan balance. Interest is the fee charged by the lender for borrowing the money. In the early years of a 30-year fixed-rate mortgage, the majority of your payment goes toward interest, while in the later years, more goes toward the principal.
Property Taxes and Insurance
Most lenders require you to pay a portion of your annual property taxes and homeowners insurance into an escrow account each month.
- Property Taxes: Assessed by your local government, usually based on the value of your property.
- Homeowners Insurance: Protects your home against damage from fire, theft, and other disasters.
HOA Fees
If you are buying a condo or a home in a planned community, you may have to pay Homeowners Association (HOA) fees. While these are usually paid directly to the association, our calculator includes them to give you a complete picture of your monthly housing obligations.
Why Use a Mortgage Calculator?
A mortgage calculator allows you to test different scenarios before you commit to a loan. By adjusting the Down Payment, you can see how putting more money upfront reduces your monthly obligation and the total interest paid over the life of the loan. Similarly, checking different Interest Rates helps you understand the impact of market fluctuations on your budget.
Example Calculation
For example, a home price of $350,000 with a 20% down payment ($70,000) leaves a loan amount of $280,000. At a 6.5% interest rate over 30 years:
- The monthly Principal & Interest would be approximately $1,770.
- Adding annual taxes of $4,500 ($375/mo) and insurance of $1,200 ($100/mo).
- The total monthly payment becomes roughly $2,245.
function calculateMortgage() {
// 1. Get input values using var
var homePrice = parseFloat(document.getElementById("homePrice").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var loanTermYears = parseFloat(document.getElementById("loanTerm").value);
var propertyTaxYearly = parseFloat(document.getElementById("propertyTax").value);
var homeInsuranceYearly = parseFloat(document.getElementById("homeInsurance").value);
var hoaFeesMonthly = parseFloat(document.getElementById("hoaFees").value);
var errorDisplay = document.getElementById("error-display");
// 2. Validate inputs
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTermYears)) {
errorDisplay.style.display = "block";
errorDisplay.textContent = "Please enter valid numbers in all required fields.";
return;
}
if (downPayment >= homePrice) {
errorDisplay.style.display = "block";
errorDisplay.textContent = "Down payment cannot be greater than or equal to the home price.";
return;
}
// Reset error message
errorDisplay.style.display = "none";
// 3. Calculation Logic
var loanAmount = homePrice – downPayment;
var monthlyInterestRate = (interestRate / 100) / 12;
var totalPayments = loanTermYears * 12;
// Calculate Monthly Principal & Interest (P&I)
// Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var monthlyPI = 0;
if (interestRate === 0) {
monthlyPI = loanAmount / totalPayments;
} else {
var x = Math.pow(1 + monthlyInterestRate, totalPayments);
monthlyPI = (loanAmount * x * monthlyInterestRate) / (x – 1);
}
// Calculate Monthly Taxes and Insurance
var monthlyTax = isNaN(propertyTaxYearly) ? 0 : propertyTaxYearly / 12;
var monthlyInsurance = isNaN(homeInsuranceYearly) ? 0 : homeInsuranceYearly / 12;
var monthlyHOA = isNaN(hoaFeesMonthly) ? 0 : hoaFeesMonthly;
// Total Monthly Payment
var totalMonthly = monthlyPI + monthlyTax + monthlyInsurance + monthlyHOA;
// Total Interest Paid
var totalAmountPaidToBank = monthlyPI * totalPayments;
var totalInterest = totalAmountPaidToBank – loanAmount;
// 4. Update the DOM
// Format as currency USD
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2,
maximumFractionDigits: 2
});
var formatterNoDec = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 0,
maximumFractionDigits: 0
});
document.getElementById("totalMonthlyPayment").innerHTML = formatter.format(totalMonthly);
document.getElementById("piPayment").innerHTML = formatter.format(monthlyPI);
document.getElementById("taxMonthly").innerHTML = formatter.format(monthlyTax);
document.getElementById("insMonthly").innerHTML = formatter.format(monthlyInsurance);
document.getElementById("hoaMonthly").innerHTML = formatter.format(monthlyHOA);
document.getElementById("totalLoanAmount").innerHTML = formatterNoDec.format(loanAmount);
document.getElementById("totalInterest").innerHTML = formatterNoDec.format(totalInterest);
}
// Initialize calculation on load so the "Result" isn't empty
window.onload = function() {
calculateMortgage();
};