#mortgage-calculator-wrapper .calc-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
background: #f9f9f9;
padding: 30px;
border-radius: 8px;
box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}
#mortgage-calculator-wrapper .input-group {
margin-bottom: 15px;
}
#mortgage-calculator-wrapper label {
display: block;
margin-bottom: 5px;
font-weight: 600;
color: #333;
}
#mortgage-calculator-wrapper input {
width: 100%;
padding: 10px;
border: 1px solid #ddd;
border-radius: 4px;
font-size: 16px;
}
#mortgage-calculator-wrapper button {
grid-column: 1 / -1;
padding: 15px;
background-color: #2c3e50;
color: white;
border: none;
border-radius: 4px;
font-size: 18px;
font-weight: bold;
cursor: pointer;
transition: background 0.3s;
margin-top: 10px;
}
#mortgage-calculator-wrapper button:hover {
background-color: #34495e;
}
#mortgage-calculator-wrapper .results-section {
grid-column: 1 / -1;
margin-top: 20px;
padding: 20px;
background: #fff;
border: 1px solid #eee;
border-radius: 4px;
display: none;
}
#mortgage-calculator-wrapper .result-row {
display: flex;
justify-content: space-between;
margin-bottom: 10px;
padding-bottom: 10px;
border-bottom: 1px solid #f0f0f0;
}
#mortgage-calculator-wrapper .result-row.total {
border-bottom: none;
font-size: 1.2em;
font-weight: bold;
color: #2c3e50;
margin-top: 10px;
}
#mortgage-calculator-wrapper .error-msg {
color: red;
grid-column: 1 / -1;
display: none;
text-align: center;
}
@media (max-width: 600px) {
#mortgage-calculator-wrapper .calc-grid {
grid-template-columns: 1fr;
}
}
#mortgage-calculator-wrapper h2, #mortgage-calculator-wrapper h3 {
color: #2c3e50;
}
#mortgage-calculator-wrapper p {
line-height: 1.6;
color: #555;
margin-bottom: 15px;
}
#mortgage-calculator-wrapper ul {
margin-bottom: 20px;
padding-left: 20px;
color: #555;
}
#mortgage-calculator-wrapper li {
margin-bottom: 8px;
}
function calculateMortgage() {
var homePrice = parseFloat(document.getElementById("homePrice").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var loanTerm = parseFloat(document.getElementById("loanTerm").value);
var propertyTax = parseFloat(document.getElementById("propertyTax").value);
var homeInsurance = parseFloat(document.getElementById("homeInsurance").value);
var hoaFees = parseFloat(document.getElementById("hoaFees").value);
var errorDisplay = document.getElementById("errorDisplay");
var resultSection = document.getElementById("resultSection");
// Input Validation
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTerm) || homePrice <= 0 || loanTerm <= 0) {
errorDisplay.style.display = "block";
resultSection.style.display = "none";
return;
}
// Defaults for optional fields
if (isNaN(propertyTax)) propertyTax = 0;
if (isNaN(homeInsurance)) homeInsurance = 0;
if (isNaN(hoaFees)) hoaFees = 0;
errorDisplay.style.display = "none";
// Core Calculations
var loanAmount = homePrice – downPayment;
var monthlyRate = (interestRate / 100) / 12;
var numberOfPayments = loanTerm * 12;
// Monthly Principal & Interest Calculation
// Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var monthlyPI = 0;
if (interestRate === 0) {
monthlyPI = loanAmount / numberOfPayments;
} else {
monthlyPI = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, numberOfPayments)) / (Math.pow(1 + monthlyRate, numberOfPayments) – 1);
}
var monthlyTax = propertyTax / 12;
var monthlyInsurance = homeInsurance / 12;
// PMI Calculation (Private Mortgage Insurance)
// Typically required if down payment is less than 20%. Estimated at 0.5% of loan amount annually.
var monthlyPMI = 0;
var equityPercent = (downPayment / homePrice) * 100;
if (equityPercent 0) {
pmiRow.style.display = "flex";
document.getElementById("displayPMI").innerText = "$" + monthlyPMI.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
} else {
pmiRow.style.display = "none";
}
document.getElementById("displayTotal").innerText = "$" + totalMonthlyPayment.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("totalInterest").innerText = "$" + totalInterestPaid.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
resultSection.style.display = "block";
}
Calculate Your Monthly Mortgage Payment
Please enter valid numeric values greater than zero for Home Price and Term.
Payment Breakdown
Principal & Interest:
$0.00
Property Tax:
$0.00
Home Insurance:
$0.00
HOA Fees:
$0.00
PMI (Est. < 20% Down):
$0.00
Total Monthly Payment:
$0.00
Total Interest Paid over Loan Life: $0.00
Understanding Your Mortgage Payment
A mortgage is likely the largest debt you will ever take on, so understanding how your monthly payment is calculated is crucial for financial planning. This calculator breaks down the total cost into its core components: Principal, Interest, Taxes, and Insurance (often referred to as PITI).
Breakdown of Costs
- Principal: The portion of your payment that goes directly towards paying down the loan balance. In the early years of a mortgage, this amount is small but grows over time.
- Interest: The cost of borrowing money paid to the lender. Initially, this makes up the majority of your monthly payment.
- Property Taxes: An annual tax levied by your local government based on the assessed value of your home. Lenders often collect this monthly and hold it in an escrow account.
- Homeowners Insurance: Insurance that covers damages to the property. Like taxes, this is often bundled into the monthly mortgage payment.
- PMI (Private Mortgage Insurance): If your down payment is less than 20% of the home's value, lenders usually require PMI to protect them against default.
How Interest Rates Affect Affordability
Even a small change in interest rates can significantly impact your monthly payment and the total interest paid over the life of the loan. For example, on a $300,000 loan, a 1% increase in interest rate can raise your monthly payment by hundreds of dollars and increase the total cost of the loan by tens of thousands.
Amortization Explained
Most fixed-rate mortgages are fully amortized. This means your total monthly payment remains the same, but the composition changes. In the beginning, you are paying mostly interest. As the loan matures, a larger portion of the payment is applied to the principal balance, accelerating your equity build-up.