Mortgage Payment Calculator
.calc-container {
max-width: 800px;
margin: 20px auto;
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
border: 1px solid #e0e0e0;
border-radius: 8px;
box-shadow: 0 4px 12px rgba(0,0,0,0.05);
background: #fff;
padding: 30px;
}
.calc-title {
text-align: center;
color: #2c3e50;
margin-bottom: 30px;
font-size: 28px;
}
.calc-wrapper {
display: flex;
flex-wrap: wrap;
gap: 30px;
}
.calc-inputs {
flex: 1;
min-width: 300px;
}
.calc-results {
flex: 1;
min-width: 300px;
background-color: #f8f9fa;
padding: 20px;
border-radius: 8px;
border: 1px solid #dee2e6;
}
.input-group {
margin-bottom: 15px;
}
.input-group label {
display: block;
margin-bottom: 5px;
font-weight: 600;
color: #495057;
font-size: 14px;
}
.input-group input, .input-group select {
width: 100%;
padding: 10px;
border: 1px solid #ced4da;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.input-group input:focus {
border-color: #007bff;
outline: none;
}
.calc-btn {
width: 100%;
padding: 12px;
background-color: #007bff;
color: white;
border: none;
border-radius: 4px;
font-size: 16px;
font-weight: bold;
cursor: pointer;
transition: background 0.2s;
margin-top: 10px;
}
.calc-btn:hover {
background-color: #0056b3;
}
.result-row {
display: flex;
justify-content: space-between;
margin-bottom: 12px;
padding-bottom: 8px;
border-bottom: 1px solid #e9ecef;
}
.result-row.total {
border-top: 2px solid #dee2e6;
border-bottom: none;
padding-top: 15px;
margin-top: 15px;
font-weight: bold;
color: #2c3e50;
font-size: 18px;
}
.result-label {
color: #6c757d;
}
.result-value {
font-weight: 600;
color: #212529;
}
.total .result-value {
color: #007bff;
}
.article-content {
max-width: 800px;
margin: 40px auto;
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
line-height: 1.6;
color: #333;
}
.article-content h2 {
color: #2c3e50;
margin-top: 30px;
}
.article-content h3 {
color: #495057;
}
.article-content p {
margin-bottom: 15px;
}
.article-content ul {
margin-bottom: 20px;
padding-left: 20px;
}
.article-content li {
margin-bottom: 8px;
}
.error-msg {
color: #dc3545;
font-size: 14px;
margin-top: 5px;
display: none;
}
/* Visual Bar for Breakdown */
.breakdown-bar {
display: flex;
height: 10px;
border-radius: 5px;
overflow: hidden;
margin: 15px 0;
}
.bar-pi { background-color: #007bff; }
.bar-tax { background-color: #28a745; }
.bar-ins { background-color: #ffc107; }
.legend {
display: flex;
gap: 15px;
font-size: 12px;
margin-bottom: 20px;
}
.legend-item { display: flex; align-items: center; gap: 5px; }
.dot { width: 10px; height: 10px; border-radius: 50%; }
Mortgage Payment Calculator
Principal & Interest:
$0.00
Property Tax:
$0.00
Home Insurance:
$0.00
Total Monthly Payment:
$0.00
Loan Amount:
$0.00
Total Interest Paid:
$0.00
Payoff Date:
–
Understanding Your Mortgage Calculation
Buying a home is one of the most significant financial decisions you will make. This Mortgage Payment Calculator helps you estimate your monthly financial commitment by factoring in principal, interest, taxes, and insurance (often referred to as PITI).
How the Formula Works
The core calculation for your monthly mortgage payment uses the standard amortization formula:
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 / 12)
- n = Number of payments over the loan's lifetime (Years * 12)
Components of Your Monthly Payment
While the formula calculates the loan repayment, your actual check written to the bank often includes more:
- Principal: The portion of money that goes toward paying down the loan balance.
- Interest: The cost of borrowing the money. In the early years of a mortgage, a higher percentage of your payment goes toward interest.
- Property Taxes: Collected by your lender and held in an escrow account to pay your local government. This calculator estimates the monthly portion based on the annual amount provided.
- Homeowners Insurance: Protects your property against damage. Like taxes, this is usually divided into monthly installments and paid via escrow.
The Impact of the Down Payment
Your down payment significantly affects your monthly payment and total loan cost. A larger down payment reduces the principal loan amount, which lowers your monthly P&I payment and reduces the total interest paid over the life of the loan. Additionally, if you put down at least 20%, you typically avoid Private Mortgage Insurance (PMI), which can otherwise add 0.5% to 1% to your annual costs.
Choosing the Right Loan Term
Most buyers choose between a 15-year and a 30-year fixed-rate mortgage. A 30-year term offers lower monthly payments, making the home more affordable month-to-month. However, a 15-year term significantly reduces the total interest paid and builds equity much faster, though the monthly obligation is higher.
function calculateMortgage() {
// 1. 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 propertyTaxAnnual = parseFloat(document.getElementById('propertyTax').value);
var homeInsuranceAnnual = parseFloat(document.getElementById('homeInsurance').value);
var errorDisplay = document.getElementById('errorDisplay');
// 2. Validate Inputs
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) ||
isNaN(propertyTaxAnnual) || isNaN(homeInsuranceAnnual) ||
homePrice < 0 || downPayment < 0 || interestRate = home price
if (loanAmount 0 && monthlyInterestRate > 0) {
monthlyPrincipalAndInterest = loanAmount *
(monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments)) /
(Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1);
} else if (loanAmount > 0 && monthlyInterestRate === 0) {
monthlyPrincipalAndInterest = loanAmount / numberOfPayments;
}
// Monthly Tax and Insurance
var monthlyTax = propertyTaxAnnual / 12;
var monthlyInsurance = homeInsuranceAnnual / 12;
// Total Monthly
var totalMonthlyPayment = monthlyPrincipalAndInterest + monthlyTax + monthlyInsurance;
// Total Interest over life of loan
var totalCostOfLoan = (monthlyPrincipalAndInterest * numberOfPayments);
var totalInterest = totalCostOfLoan – loanAmount;
// Payoff Date
var today = new Date();
var payoffYear = today.getFullYear() + loanTermYears;
var payoffMonth = today.toLocaleString('default', { month: 'short' });
var payoffDateString = payoffMonth + " " + payoffYear;
// 4. Update UI
// Formatter
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
});
document.getElementById('resultPI').innerText = formatter.format(monthlyPrincipalAndInterest);
document.getElementById('resultTax').innerText = formatter.format(monthlyTax);
document.getElementById('resultIns').innerText = formatter.format(monthlyInsurance);
document.getElementById('resultTotal').innerText = formatter.format(totalMonthlyPayment);
document.getElementById('resultLoanAmount').innerText = formatter.format(loanAmount);
document.getElementById('resultTotalInterest').innerText = formatter.format(totalInterest > 0 ? totalInterest : 0);
document.getElementById('resultPayoffDate').innerText = payoffDateString;
// Update Breakdown Bar
if (totalMonthlyPayment > 0) {
var piPercent = (monthlyPrincipalAndInterest / totalMonthlyPayment) * 100;
var taxPercent = (monthlyTax / totalMonthlyPayment) * 100;
var insPercent = (monthlyInsurance / totalMonthlyPayment) * 100;
document.querySelector('.bar-pi').style.width = piPercent + "%";
document.querySelector('.bar-tax').style.width = taxPercent + "%";
document.querySelector('.bar-ins').style.width = insPercent + "%";
}
}
// Initialize calculation on load
window.onload = function() {
calculateMortgage();
};