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;
}
.calculator-container {
background-color: #f8f9fa;
border: 1px solid #e9ecef;
border-radius: 8px;
padding: 30px;
margin-bottom: 40px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.calc-title {
text-align: center;
color: #2c3e50;
margin-bottom: 25px;
}
.calc-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
}
@media (max-width: 768px) {
.calc-grid {
grid-template-columns: 1fr;
}
}
.input-group {
margin-bottom: 15px;
}
.input-group label {
display: block;
margin-bottom: 5px;
font-weight: 600;
font-size: 0.95rem;
}
.input-group input {
width: 100%;
padding: 10px;
border: 1px solid #ced4da;
border-radius: 4px;
font-size: 1rem;
box-sizing: border-box;
}
.input-group input:focus {
border-color: #4a90e2;
outline: none;
}
.calc-btn {
grid-column: 1 / -1;
background-color: #0056b3;
color: white;
border: none;
padding: 15px;
font-size: 1.1rem;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
transition: background-color 0.2s;
margin-top: 10px;
width: 100%;
}
.calc-btn:hover {
background-color: #004494;
}
#result-box {
grid-column: 1 / -1;
background-color: #ffffff;
border: 1px solid #dee2e6;
border-radius: 4px;
padding: 20px;
margin-top: 20px;
display: none;
}
.result-row {
display: flex;
justify-content: space-between;
margin-bottom: 10px;
padding-bottom: 10px;
border-bottom: 1px solid #eee;
}
.result-row.total {
border-bottom: none;
font-weight: bold;
font-size: 1.2rem;
color: #0056b3;
margin-top: 10px;
padding-top: 10px;
border-top: 2px solid #0056b3;
}
.article-content {
margin-top: 50px;
background: #fff;
}
.article-content h2 {
color: #2c3e50;
border-bottom: 2px solid #eee;
padding-bottom: 10px;
margin-top: 30px;
}
.article-content h3 {
color: #34495e;
margin-top: 25px;
}
.article-content p {
margin-bottom: 15px;
}
.error-msg {
color: #dc3545;
font-weight: bold;
text-align: center;
margin-top: 10px;
display: none;
}
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 errorDiv = document.getElementById("error-message");
var resultDiv = document.getElementById("result-box");
// Validate inputs
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTerm) || isNaN(propertyTax) || isNaN(homeInsurance) || homePrice <= 0 || loanTerm <= 0) {
errorDiv.style.display = "block";
resultDiv.style.display = "none";
return;
}
errorDiv.style.display = "none";
// Loan amount calculation
var principal = homePrice – downPayment;
// Handle case where down payment exceeds home price
if (principal < 0) {
principal = 0;
}
// Monthly interest rate calculation
var monthlyRate = (interestRate / 100) / 12;
var numberOfPayments = loanTerm * 12;
// Calculate Principal and Interest (P&I)
var monthlyPI = 0;
if (monthlyRate === 0) {
monthlyPI = principal / numberOfPayments;
} else {
monthlyPI = principal * (monthlyRate * Math.pow(1 + monthlyRate, numberOfPayments)) / (Math.pow(1 + monthlyRate, numberOfPayments) – 1);
}
// Calculate Taxes and Insurance
var monthlyTax = propertyTax / 12;
var monthlyIns = homeInsurance / 12;
// Total Monthly Payment
var totalMonthly = monthlyPI + monthlyTax + monthlyIns;
// Total Interest
var totalPaymentOverTerm = monthlyPI * numberOfPayments;
var totalInterest = totalPaymentOverTerm – principal;
// Format and Display Results
document.getElementById("res-pi").innerText = "$" + monthlyPI.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("res-tax").innerText = "$" + monthlyTax.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("res-ins").innerText = "$" + monthlyIns.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("res-total").innerText = "$" + totalMonthly.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("res-loan-amount").innerText = "$" + principal.toLocaleString('en-US', {minimumFractionDigits: 0, maximumFractionDigits: 0});
document.getElementById("res-total-interest").innerText = "$" + totalInterest.toLocaleString('en-US', {minimumFractionDigits: 0, maximumFractionDigits: 0});
resultDiv.style.display = "block";
}
Understanding Your Monthly Mortgage Payment (PITI)
When you take out a mortgage to buy a home, the monthly check you write covers more than just paying back the money you borrowed. In the real estate industry, a comprehensive mortgage payment is often referred to as PITI, which stands for Principal, Interest, Taxes, and Insurance. Using a calculator that breaks down these components is essential for determining true home affordability.
1. Principal
The principal is the portion of your payment that goes directly toward reducing the outstanding balance of your loan. In the early years of a typical 30-year fixed-rate mortgage, the principal portion of your payment is small, while the interest portion is high. As time passes, this shifts, and you begin to pay down the principal faster.
2. Interest
Interest is the fee the lender charges for loaning you the money. It is calculated based on your annual interest rate and your remaining loan balance. A lower interest rate can save you tens of thousands of dollars over the life of the loan. For example, on a $300,000 loan, a 1% difference in interest rate can change your monthly payment by over $180.
3. Property Taxes
Property taxes are assessed by your local government to fund public services like schools, police, and road maintenance. Lenders typically collect this money from you in monthly installments (1/12th of your annual bill) and hold it in an escrow account to pay the tax bill when it is due. Property taxes can vary significantly by location, often ranging from 0.5% to over 2.5% of the property's assessed value annually.
4. Homeowners Insurance
Lenders require you to carry homeowners insurance to protect the property against damage from fire, storms, and other hazards. Like property taxes, the premium is usually divided into monthly payments and collected via escrow. This ensures that the asset securing the loan remains protected.
How the Down Payment Affects Your Mortgage
Your down payment plays a critical role in your monthly costs. A larger down payment reduces the principal loan amount, which lowers your monthly Principal & Interest payment. Additionally, if you put down less than 20% of the home's purchase price, lenders often require Private Mortgage Insurance (PMI), which is an extra monthly fee not calculated in standard PITI but important to consider.
Fixed vs. Adjustable Rate Mortgages
The calculator above assumes a Fixed-Rate Mortgage, where the interest rate remains the same for the entire loan term (usually 15 or 30 years). This provides stability as your Principal & Interest payment will never change. In contrast, an Adjustable-Rate Mortgage (ARM) has an interest rate that can fluctuate after an initial fixed period, potentially increasing your monthly financial obligation.
Using This Calculator for Budgeting
To get the most accurate estimate from the Mortgage Payment Calculator above, try to find the specific property tax rate for the county where you are looking to buy. While the national average for property tax is around 1.1%, specific areas can be much higher. Similarly, insurance quotes can vary based on the age of the home and local risks (like flood zones). Inputting realistic numbers for taxes and insurance is crucial, as these two components can add 30-40% to your base mortgage payment.