.mortgage-calculator-wrapper {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 0 auto;
color: #333;
line-height: 1.6;
}
.calc-container {
background: #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-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
}
@media (max-width: 600px) {
.calc-grid {
grid-template-columns: 1fr;
}
}
.input-group {
margin-bottom: 15px;
}
.input-group label {
display: block;
margin-bottom: 5px;
font-weight: 600;
font-size: 0.9rem;
color: #495057;
}
.input-group input, .input-group select {
width: 100%;
padding: 10px;
border: 1px solid #ced4da;
border-radius: 4px;
font-size: 1rem;
box-sizing: border-box;
}
.input-group input:focus {
outline: none;
border-color: #0056b3;
box-shadow: 0 0 0 2px rgba(0,86,179,0.1);
}
.calc-btn {
background-color: #0056b3;
color: white;
border: none;
padding: 12px 20px;
font-size: 1rem;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
width: 100%;
margin-top: 10px;
transition: background-color 0.2s;
}
.calc-btn:hover {
background-color: #004494;
}
.results-section {
background: #fff;
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:last-child {
border-bottom: none;
margin-bottom: 0;
padding-bottom: 0;
}
.result-label {
color: #6c757d;
}
.result-value {
font-weight: bold;
font-size: 1.1rem;
}
.result-main {
text-align: center;
margin-bottom: 20px;
background: #e7f1ff;
padding: 15px;
border-radius: 4px;
color: #004085;
}
.result-main h3 {
margin: 0 0 5px 0;
font-size: 0.9rem;
text-transform: uppercase;
letter-spacing: 1px;
}
.result-main .big-number {
font-size: 2rem;
font-weight: 800;
}
.error-msg {
color: #dc3545;
text-align: center;
margin-top: 10px;
display: none;
}
.article-content h2 {
font-size: 1.5rem;
margin-top: 30px;
color: #2c3e50;
border-bottom: 2px solid #0056b3;
padding-bottom: 10px;
display: inline-block;
}
.article-content p {
margin-bottom: 15px;
}
.article-content ul {
margin-bottom: 20px;
padding-left: 20px;
}
.article-content li {
margin-bottom: 10px;
}
function calculateMortgage() {
// Get input elements by ID
var homePriceInput = document.getElementById("homePrice");
var downPaymentInput = document.getElementById("downPayment");
var interestRateInput = document.getElementById("interestRate");
var loanTermInput = document.getElementById("loanTerm");
var propertyTaxInput = document.getElementById("propertyTax");
var homeInsuranceInput = document.getElementById("homeInsurance");
// Parse values
var homePrice = parseFloat(homePriceInput.value);
var downPayment = parseFloat(downPaymentInput.value);
var interestRate = parseFloat(interestRateInput.value);
var loanTermYears = parseInt(loanTermInput.value);
var yearlyTax = parseFloat(propertyTaxInput.value);
var yearlyInsurance = parseFloat(homeInsuranceInput.value);
// Error Handling elements
var errorMsg = document.getElementById("errorMsg");
var resultsSection = document.getElementById("resultsSection");
// Validate inputs
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTermYears)) {
errorMsg.style.display = "block";
resultsSection.style.display = "none";
return;
}
// Optional fields default to 0 if empty
if (isNaN(yearlyTax)) yearlyTax = 0;
if (isNaN(yearlyInsurance)) yearlyInsurance = 0;
// Logic Validation
if (downPayment > homePrice) {
alert("Down payment cannot be greater than home price.");
return;
}
errorMsg.style.display = "none";
// Calculation Logic
var principal = homePrice – downPayment;
var monthlyInterestRate = (interestRate / 100) / 12;
var numberOfPayments = loanTermYears * 12;
// Calculate Principal & Interest (P&I)
var monthlyPrincipalInterest = 0;
if (interestRate === 0) {
monthlyPrincipalInterest = principal / numberOfPayments;
} else {
var x = Math.pow(1 + monthlyInterestRate, numberOfPayments);
monthlyPrincipalInterest = (principal * x * monthlyInterestRate) / (x – 1);
}
// Calculate Escrow items (Tax & Insurance)
var monthlyTax = yearlyTax / 12;
var monthlyInsurance = yearlyInsurance / 12;
// Totals
var totalMonthlyPayment = monthlyPrincipalInterest + monthlyTax + monthlyInsurance;
var totalPaymentOverLife = (monthlyPrincipalInterest * numberOfPayments);
var totalInterestPaid = totalPaymentOverLife – principal;
var totalCostOfLoan = totalPaymentOverLife + (yearlyTax * loanTermYears) + (yearlyInsurance * loanTermYears);
// Display Results
// Helper function for formatting currency
function formatMoney(amount) {
return "$" + amount.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
}
document.getElementById("monthlyTotalDisplay").innerHTML = formatMoney(totalMonthlyPayment);
document.getElementById("piDisplay").innerHTML = formatMoney(monthlyPrincipalInterest);
document.getElementById("taxDisplay").innerHTML = formatMoney(monthlyTax);
document.getElementById("insuranceDisplay").innerHTML = formatMoney(monthlyInsurance);
document.getElementById("totalInterestDisplay").innerHTML = formatMoney(totalInterestPaid);
document.getElementById("totalCostDisplay").innerHTML = formatMoney(totalCostOfLoan);
resultsSection.style.display = "block";
}
30 Years
20 Years
15 Years
10 Years
Please enter valid numeric values for all fields.
Estimated Monthly Payment
$0.00
Principal & Interest:
$0.00
Property Tax (Monthly):
$0.00
Home Insurance (Monthly):
$0.00
Total Interest Paid (Over Term):
$0.00
Total Cost of Loan:
$0.00
Understanding Your Mortgage Calculation
Purchasing a home is one of the most significant financial decisions you will make. This Mortgage Calculator helps you estimate your monthly financial commitment by breaking down the costs associated with a home loan. Unlike simple loan calculators, this tool accounts for the "PITI" components: Principal, Interest, Taxes, and Insurance.
How the Calculation Works
The core of a mortgage payment calculation determines the Principal and Interest (P&I). This is calculated using the standard amortization formula:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
- M = Total monthly P&I payment
- P = Principal loan amount (Home Price minus Down Payment)
- i = Monthly interest rate (Annual rate divided by 12)
- n = Number of months (Loan term in years multiplied by 12)
Components of Your Monthly Payment
While the bank requires the principal and interest, your actual monthly housing cost often includes other factors:
- Principal: The portion of your payment that reduces the loan balance.
- Interest: The cost of borrowing money, paid to the lender. In the early years of a mortgage, a larger portion of your payment goes toward interest.
- Property Taxes: Assessed by your local government. Lenders often collect this monthly and place it in an escrow account to pay the bill annually on your behalf.
- Homeowners Insurance: Protects your property against damage. Like taxes, this is often collected monthly in escrow.
Why the Down Payment Matters
Your down payment directly impacts your monthly rate. A larger down payment reduces the principal loan amount (P), which lowers both your monthly payment and the total interest paid over the life of the loan. For example, putting down 20% typically avoids Private Mortgage Insurance (PMI), though this calculator focuses on the standard PITI components.
Interest Rates and Loan Terms
Even a small difference in interest rates can save (or cost) you thousands of dollars over a 30-year term. Additionally, choosing a shorter loan term (e.g., 15 years vs. 30 years) will increase your monthly payment but significantly decrease the total interest paid, allowing you to build equity faster.