.calculator-wrapper {
max-width: 800px;
margin: 0 auto;
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
color: #333;
line-height: 1.6;
}
.calc-container {
background-color: #f9f9f9;
border: 1px solid #e0e0e0;
border-radius: 8px;
padding: 30px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
margin-bottom: 40px;
}
.calc-header {
text-align: center;
margin-bottom: 25px;
color: #2c3e50;
}
.calc-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
}
.calc-input-group {
margin-bottom: 15px;
}
.calc-input-group label {
display: block;
margin-bottom: 5px;
font-weight: 600;
font-size: 14px;
}
.calc-input-group input, .calc-input-group select {
width: 100%;
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box; /* Fixes padding width issues */
}
.calc-input-group input:focus {
border-color: #3498db;
outline: none;
}
.calc-btn {
grid-column: span 2;
background-color: #2980b9;
color: white;
border: none;
padding: 15px;
font-size: 18px;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
transition: background 0.3s;
margin-top: 10px;
}
.calc-btn:hover {
background-color: #1f618d;
}
.calc-results {
grid-column: span 2;
background-color: #fff;
border: 1px solid #dcdcdc;
padding: 20px;
border-radius: 4px;
margin-top: 20px;
display: none; /* Hidden by default */
}
.result-row {
display: flex;
justify-content: space-between;
padding: 8px 0;
border-bottom: 1px solid #eee;
}
.result-row:last-child {
border-bottom: none;
}
.result-row.total {
font-weight: 700;
font-size: 1.2em;
color: #27ae60;
border-top: 2px solid #eee;
padding-top: 15px;
}
.calc-article {
margin-top: 50px;
padding: 0 10px;
}
.calc-article h2 {
color: #2c3e50;
border-bottom: 2px solid #3498db;
padding-bottom: 10px;
margin-top: 30px;
}
.calc-article h3 {
color: #34495e;
margin-top: 25px;
}
.calc-article p {
margin-bottom: 15px;
}
.calc-article ul {
margin-bottom: 15px;
padding-left: 20px;
}
.calc-article li {
margin-bottom: 8px;
}
@media (max-width: 600px) {
.calc-grid {
grid-template-columns: 1fr;
}
.calc-btn, .calc-results {
grid-column: span 1;
}
}
function calculateMortgage() {
// Get Input Values
var homePrice = parseFloat(document.getElementById('mc-home-price').value);
var downPayment = parseFloat(document.getElementById('mc-down-payment').value);
var interestRate = parseFloat(document.getElementById('mc-interest-rate').value);
var loanTermYears = parseInt(document.getElementById('mc-loan-term').value);
var annualTax = parseFloat(document.getElementById('mc-property-tax').value);
var annualInsurance = parseFloat(document.getElementById('mc-home-insurance').value);
// Validation
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTermYears) || isNaN(annualTax) || isNaN(annualInsurance)) {
alert("Please enter valid numbers in all fields.");
return;
}
if (downPayment >= homePrice) {
alert("Down payment cannot be greater than or equal to the home price.");
return;
}
// Core Calculations
var loanAmount = homePrice – downPayment;
var monthlyInterestRate = (interestRate / 100) / 12;
var totalPayments = loanTermYears * 12;
// Monthly Principal & Interest (P&I) Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var monthlyPrincipalInterest;
if (interestRate === 0) {
monthlyPrincipalInterest = loanAmount / totalPayments;
} else {
monthlyPrincipalInterest = loanAmount * (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, totalPayments)) / (Math.pow(1 + monthlyInterestRate, totalPayments) – 1);
}
// Monthly Taxes and Insurance (T&I)
var monthlyTax = annualTax / 12;
var monthlyInsurance = annualInsurance / 12;
// Total PITI
var totalMonthlyPayment = monthlyPrincipalInterest + monthlyTax + monthlyInsurance;
// Total Interest Paid over Life of Loan
var totalCostOfLoan = monthlyPrincipalInterest * totalPayments;
var totalInterest = totalCostOfLoan – loanAmount;
// Format Currency
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
// Update DOM
document.getElementById('res-principal-interest').innerText = formatter.format(monthlyPrincipalInterest);
document.getElementById('res-monthly-tax').innerText = formatter.format(monthlyTax);
document.getElementById('res-monthly-ins').innerText = formatter.format(monthlyInsurance);
document.getElementById('res-total-monthly').innerText = formatter.format(totalMonthlyPayment);
document.getElementById('res-loan-amount').innerText = formatter.format(loanAmount);
document.getElementById('res-total-interest').innerText = formatter.format(totalInterest);
// Show Results
document.getElementById('mc-results-box').style.display = 'block';
}
Understanding Your Mortgage PITI Payment
When planning to purchase a home, looking at the listing price is only the tip of the iceberg. To truly understand affordability, you must calculate your monthly PITI payment. This comprehensive Mortgage PITI Calculator breaks down your costs into four critical components: Principal, Interest, Taxes, and Insurance.
What is PITI?
PITI stands for the four main elements that make up your monthly mortgage bill:
- Principal: The portion of your payment that goes directly toward paying down the loan balance (the amount you borrowed).
- Interest: The cost of borrowing money paid to the lender. In the early years of a mortgage, a significant percentage of your payment goes toward interest rather than principal.
- Taxes: Property taxes assessed by your local government. Lenders often collect this monthly and hold it in an escrow account to pay the bill annually on your behalf.
- Insurance: Homeowners insurance protects your property against damage. Like taxes, this is usually collected monthly into an escrow account.
How Interest Rates Affect Your Buying Power
Even a small change in interest rates can drastically alter your monthly obligation. For example, on a $300,000 loan, a 1% increase in interest rate can increase your monthly payment by hundreds of dollars. Using the calculator above, you can test different "Interest Rate" scenarios to see how sensitive your budget is to market fluctuations.
The Role of the Loan Term
Most homebuyers choose between a 15-year and a 30-year fixed-rate mortgage.
30-Year Term: Offers lower monthly payments because the repayment is spread over a longer period, but you will pay significantly more in total interest.
15-Year Term: Comes with higher monthly payments, but you build equity faster and pay far less interest over the life of the loan.
Estimating Taxes and Insurance
While Principal and Interest are calculated based on math formulas, Taxes and Insurance are variables based on location and property specifics.
Property Tax Tip: A national average estimate is often around 1.1% of the home's value per year, but this varies wildly by state (e.g., NJ is higher, HI is lower).
Insurance Tip: Annual homeowners insurance typically costs between $800 and $2,000 depending on coverage levels and regional risks (like hurricanes or wildfires).
Use this calculator as a starting point for your home-buying journey. By inputting realistic numbers for taxes and insurance, you avoid "payment shock" and ensure your dream home fits comfortably within your financial goals.