/* Calculator Styles */
.calc-container {
max-width: 800px;
margin: 0 auto;
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
color: #333;
background: #f9f9f9;
padding: 30px;
border-radius: 8px;
box-shadow: 0 4px 15px rgba(0,0,0,0.1);
}
.calc-header {
text-align: center;
margin-bottom: 30px;
}
.calc-header h2 {
color: #2c3e50;
margin-bottom: 10px;
}
.calc-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
}
@media (max-width: 600px) {
.calc-grid {
grid-template-columns: 1fr;
}
}
.calc-group {
display: flex;
flex-direction: column;
}
.calc-group label {
font-weight: 600;
margin-bottom: 5px;
font-size: 14px;
color: #555;
}
.calc-input-wrapper {
position: relative;
}
.calc-input-wrapper span {
position: absolute;
left: 10px;
top: 50%;
transform: translateY(-50%);
color: #777;
}
.calc-input-wrapper input {
width: 100%;
padding: 10px 10px 10px 25px;
border: 1px solid #ddd;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.calc-input-wrapper input:focus {
border-color: #3498db;
outline: none;
}
.calc-btn {
grid-column: 1 / -1;
background-color: #3498db;
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: #2980b9;
}
.calc-results {
margin-top: 30px;
background: #fff;
padding: 20px;
border-radius: 4px;
border-left: 5px solid #3498db;
display: none; /* Hidden by default */
}
.result-row {
display: flex;
justify-content: space-between;
padding: 10px 0;
border-bottom: 1px solid #eee;
}
.result-row:last-child {
border-bottom: none;
}
.result-label {
color: #666;
}
.result-value {
font-weight: bold;
color: #2c3e50;
font-size: 18px;
}
.main-result {
text-align: center;
padding: 20px;
background-color: #e8f6f3;
border-radius: 5px;
margin-bottom: 20px;
}
.main-result h3 {
margin: 0;
font-size: 16px;
color: #16a085;
text-transform: uppercase;
letter-spacing: 1px;
}
.main-result .big-number {
font-size: 36px;
color: #16a085;
font-weight: 800;
margin-top: 10px;
display: block;
}
/* Article Content Styles */
.content-container {
max-width: 800px;
margin: 40px auto;
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
line-height: 1.6;
color: #333;
}
.content-container h2 {
color: #2c3e50;
border-bottom: 2px solid #3498db;
padding-bottom: 10px;
margin-top: 40px;
}
.content-container h3 {
color: #34495e;
margin-top: 25px;
}
.content-container p {
margin-bottom: 15px;
}
.content-container ul {
margin-bottom: 20px;
padding-left: 20px;
}
.content-container li {
margin-bottom: 8px;
}
.highlight-box {
background-color: #f0f7fb;
border-left: 4px solid #3498db;
padding: 15px;
margin: 20px 0;
}
function calculateMortgage() {
// 1. 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 years = parseFloat(document.getElementById("mc-loan-term").value);
var annualTax = parseFloat(document.getElementById("mc-property-tax").value);
var annualInsurance = parseFloat(document.getElementById("mc-insurance").value);
// 2. Validation
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) || isNaN(years) ||
homePrice <= 0 || years <= 0) {
alert("Please enter valid positive numbers for Home Price and Loan Term.");
return;
}
// 3. Core Calculation Logic
var principal = homePrice – downPayment;
var monthlyInterestRate = (interestRate / 100) / 12;
var numberOfPayments = years * 12;
var monthlyPrincipalAndInterest = 0;
// Handle zero interest rate edge case
if (interestRate === 0) {
monthlyPrincipalAndInterest = principal / numberOfPayments;
} else {
// Standard Mortgage Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var pow = Math.pow(1 + monthlyInterestRate, numberOfPayments);
monthlyPrincipalAndInterest = principal * ((monthlyInterestRate * pow) / (pow – 1));
}
var monthlyTax = isNaN(annualTax) ? 0 : annualTax / 12;
var monthlyInsurance = isNaN(annualInsurance) ? 0 : annualInsurance / 12;
var totalMonthlyPayment = monthlyPrincipalAndInterest + monthlyTax + monthlyInsurance;
var totalRepaid = (monthlyPrincipalAndInterest * numberOfPayments) + (monthlyTax * numberOfPayments) + (monthlyInsurance * numberOfPayments);
// Total interest is total payments (P&I only) minus the loan amount
var totalInterestCost = (monthlyPrincipalAndInterest * numberOfPayments) – principal;
// 4. Update UI
// Helper function for currency formatting
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
document.getElementById("mc-monthly-payment").innerHTML = formatter.format(totalMonthlyPayment);
document.getElementById("mc-pi").innerHTML = formatter.format(monthlyPrincipalAndInterest);
document.getElementById("mc-tax-monthly").innerHTML = formatter.format(monthlyTax);
document.getElementById("mc-ins-monthly").innerHTML = formatter.format(monthlyInsurance);
document.getElementById("mc-total-repaid").innerHTML = formatter.format(totalRepaid); // Includes tax/ins
document.getElementById("mc-total-interest").innerHTML = formatter.format(totalInterestCost);
// Show results
document.getElementById("mc-results-area").style.display = "block";
}
Understanding Your Mortgage Calculation
Buying a home is one of the most significant financial decisions you will make in your lifetime. Understanding how your mortgage payment is calculated is crucial for budgeting and long-term financial planning. Our Mortgage Payment Calculator breaks down your monthly obligations, helping you see exactly where your money goes every month.
How the Mortgage Formula Works
While the calculator handles the heavy lifting, understanding the underlying math can empower your decision-making. The standard formula used by lenders to calculate monthly amortization is:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
- M = Total monthly payment
- P = Principal loan amount (Home Price minus Down Payment)
- i = Monthly interest rate (Annual Rate divided by 12)
- n = Number of payments (Loan term in years multiplied by 12)
Key Factors Affecting Your Payment
Several variables influence your monthly housing costs. Adjusting any of these in the calculator above will show you the impact on your budget.
1. Principal Loan Amount
This is the amount of money you borrow. It is calculated by taking the home's purchase price and subtracting your down payment. A larger down payment reduces your principal, which in turn lowers your monthly payment and the total interest paid over the life of the loan.
2. Interest Rate
The interest rate is the cost of borrowing money, expressed as a percentage. Even a small difference in the interest rate can result in savings or costs amounting to tens of thousands of dollars over a 30-year term. Rates fluctuate based on the economy and your personal credit score.
3. Loan Term
The loan term is the duration over which you agree to repay the loan. The most common terms are 15 and 30 years. A 30-year term usually offers lower monthly payments but results in higher total interest costs. Conversely, a 15-year term has higher monthly payments but saves significantly on interest.
4. Taxes and Insurance (Escrow)
Most mortgage payments include more than just principal and interest. Lenders often collect Property Taxes and Homeowners Insurance premiums monthly, holding them in an escrow account to pay the bills when they are due.
Real-World Calculation Example
Let's look at a realistic scenario to understand the costs. Suppose you purchase a home for $350,000.
- Down Payment: 20% ($70,000), leaving a loan amount of $280,000.
- Interest Rate: 6.5%.
- Term: 30 years.
Using the formula, your Principal and Interest payment would be approximately $1,769.82. If you add estimated property taxes of $250/month and insurance of $100/month, your total monthly outlay becomes $2,119.82.
Over the full 30 years, you would pay a total of approximately $357,135 in interest alone, assuming you make minimum payments and do not refinance.
Frequently Asked Questions
What is PMI?
Private Mortgage Insurance (PMI) is usually required if your down payment is less than 20% of the home's value. It protects the lender if you default. This calculator does not automatically add PMI, but you can estimate it and add it to the "Home Insurance" field for a rough total.
Should I choose a 15-year or 30-year mortgage?
If your budget allows for higher monthly payments, a 15-year mortgage will build equity faster and save you money on interest. However, a 30-year mortgage provides more flexibility with lower required monthly payments, allowing you to invest the difference elsewhere if you choose.