.calculator-container {
max-width: 800px;
margin: 0 auto;
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
color: #333;
line-height: 1.6;
}
.calc-box {
background: #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-title {
text-align: center;
color: #2c3e50;
margin-bottom: 25px;
font-size: 24px;
font-weight: 700;
}
.input-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
}
.input-group {
margin-bottom: 15px;
}
.input-group label {
display: block;
margin-bottom: 5px;
font-weight: 600;
font-size: 14px;
color: #555;
}
.input-group input, .input-group select {
width: 100%;
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.input-group input:focus {
border-color: #3498db;
outline: none;
box-shadow: 0 0 5px rgba(52,152,219,0.3);
}
.calc-btn {
grid-column: span 2;
background-color: #27ae60;
color: white;
border: none;
padding: 15px;
font-size: 18px;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
transition: background 0.3s;
margin-top: 10px;
width: 100%;
}
.calc-btn:hover {
background-color: #219150;
}
.results-section {
grid-column: span 2;
background: #fff;
border: 1px solid #ddd;
border-radius: 4px;
padding: 20px;
margin-top: 20px;
display: none;
}
.result-row {
display: flex;
justify-content: space-between;
padding: 10px 0;
border-bottom: 1px solid #eee;
}
.result-row:last-child {
border-bottom: none;
font-weight: bold;
font-size: 1.2em;
color: #2980b9;
}
.content-section h2 {
color: #2c3e50;
margin-top: 30px;
border-bottom: 2px solid #eee;
padding-bottom: 10px;
}
.content-section p {
margin-bottom: 15px;
}
.content-section ul {
margin-bottom: 20px;
padding-left: 20px;
}
.content-section li {
margin-bottom: 8px;
}
@media (max-width: 600px) {
.input-grid {
grid-template-columns: 1fr;
}
.calc-btn, .results-section {
grid-column: span 1;
}
}
function calculateMortgage() {
// Get Input Values
var homePrice = parseFloat(document.getElementById("homePrice").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var loanTermYears = parseInt(document.getElementById("loanTerm").value);
var propertyTax = parseFloat(document.getElementById("propertyTax").value);
var homeInsurance = parseFloat(document.getElementById("homeInsurance").value);
// Validation
if (isNaN(homePrice) || homePrice <= 0) {
alert("Please enter a valid Home Price.");
return;
}
if (isNaN(downPayment) || downPayment < 0) {
downPayment = 0;
}
if (isNaN(interestRate) || interestRate < 0) {
alert("Please enter a valid Interest Rate.");
return;
}
if (isNaN(propertyTax)) propertyTax = 0;
if (isNaN(homeInsurance)) homeInsurance = 0;
// Calculations
var principal = homePrice – downPayment;
if (principal <= 0) {
alert("Down payment cannot equal or exceed home price for a mortgage calculation.");
return;
}
// Monthly Interest Rate (r) and Total Number of Payments (n)
var r = (interestRate / 100) / 12;
var n = loanTermYears * 12;
var monthlyPrincipalInterest = 0;
// Handle 0% interest edge case
if (interestRate === 0) {
monthlyPrincipalInterest = principal / n;
} else {
// Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
monthlyPrincipalInterest = principal * ( (r * Math.pow(1 + r, n)) / (Math.pow(1 + r, n) – 1) );
}
// Calculate Escrow (Taxes and Insurance per month)
var monthlyTax = propertyTax / 12;
var monthlyInsurance = homeInsurance / 12;
var totalEscrow = monthlyTax + monthlyInsurance;
var totalMonthlyPayment = monthlyPrincipalInterest + totalEscrow;
// Display Results
document.getElementById("results").style.display = "block";
// Format currency
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
});
document.getElementById("resPrincipalInterest").innerHTML = formatter.format(monthlyPrincipalInterest);
document.getElementById("resEscrow").innerHTML = formatter.format(totalEscrow);
document.getElementById("resLoanAmount").innerHTML = formatter.format(principal);
document.getElementById("resTotal").innerHTML = formatter.format(totalMonthlyPayment);
}
Understanding Your Mortgage Payment
Purchasing a home is one of the most significant financial decisions you will make. This Mortgage Payment Calculator is designed to give you a clear, comprehensive breakdown of what your monthly housing costs will look like. Unlike simple calculators that only look at principal and interest, this tool factors in the critical "escrow" components: property taxes and homeowners insurance.
The Four Pillars of a Mortgage (PITI)
To accurately budget for your new home, it is essential to understand the four components that make up your monthly payment, often referred to by the acronym PITI:
- Principal: This is the portion of your payment that goes directly toward paying down the loan balance (the price of the home minus your down payment). In the early years of a mortgage, this amount is small, but it grows over time.
- Interest: This is the cost of borrowing money from the lender. Your interest rate and credit score heavily influence this number. A significant portion of your payment in the first decade of your loan goes purely to interest.
- Taxes: Property taxes are assessed by your local government to fund schools, roads, and public services. Lenders typically collect this monthly and hold it in an escrow account to pay the tax bill when it is due.
- Insurance: Homeowners insurance protects your property against damage. Like taxes, this is usually collected monthly by the lender and paid on your behalf annually.
How Interest Rates Affect Affordability
Even a small change in interest rates can drastically alter your monthly payment and the total cost of the loan. For example, on a $300,000 loan, a 1% difference in the interest rate can change your monthly payment by hundreds of dollars and your total interest paid over 30 years by nearly $100,000. Use the "Interest Rate" field in the calculator above to see how different rates impact your budget.
Choosing the Right Loan Term
While the standard mortgage term in the United States is 30 years, choosing a 15-year term can save you a substantial amount of money. A 15-year mortgage comes with higher monthly payments because you are paying off the principal faster, but it typically offers a lower interest rate and significantly reduces the total interest paid over the life of the loan. Use the dropdown menu in the calculator to compare 15-year vs. 30-year payment scenarios.
Next Steps
Once you have an estimate of your monthly payment, compare it to your gross monthly income. Financial experts generally recommend that your total housing payment (PITI) should not exceed 28% of your pre-tax income. This ensures you have enough room in your budget for savings, maintenance, and other life expenses.