Mortgage Payment Calculator
:root {
–primary-color: #2c3e50;
–accent-color: #3498db;
–bg-color: #f4f7f6;
–text-color: #333;
–border-radius: 8px;
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body {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
line-height: 1.6;
color: var(–text-color);
background-color: var(–bg-color);
margin: 0;
padding: 20px;
}
.calculator-container {
max-width: 800px;
margin: 0 auto;
background: #fff;
padding: 40px;
border-radius: var(–border-radius);
box-shadow: 0 4px 6px rgba(0,0,0,0.1);
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h1, h2, h3 {
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.calc-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
margin-bottom: 30px;
}
.input-group {
display: flex;
flex-direction: column;
}
.input-group label {
font-weight: 600;
margin-bottom: 5px;
font-size: 0.9rem;
}
.input-wrapper {
position: relative;
}
.input-wrapper input {
width: 100%;
padding: 10px 10px 10px 35px;
font-size: 1rem;
border: 1px solid #ddd;
border-radius: 4px;
box-sizing: border-box;
}
.input-wrapper .symbol {
position: absolute;
left: 12px;
top: 50%;
transform: translateY(-50%);
color: #777;
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.full-width {
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button {
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color: white;
border: none;
padding: 15px 30px;
font-size: 1.1rem;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
width: 100%;
transition: background-color 0.2s;
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button:hover {
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#results {
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border: 1px solid #e9ecef;
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margin-top: 30px;
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.content-section {
margin-top: 50px;
border-top: 2px solid #eee;
padding-top: 30px;
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@media (max-width: 600px) {
.calc-grid {
grid-template-columns: 1fr;
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.full-width {
grid-column: span 1;
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}
Mortgage Payment Calculator
Estimate your monthly mortgage payments effectively by inputting your loan details below. This tool calculates principal and interest based on current housing market standards.
Calculation Results
Monthly Payment (PI):
–
Loan Amount:
–
Total Interest Paid:
–
Total Cost of Loan:
–
Payoff Date:
–
Understanding Your Mortgage Calculation
Purchasing a home is one of the most significant financial decisions you will make. Understanding how your monthly mortgage payment is calculated is crucial for budgeting and financial planning. This calculator uses the standard amortization formula to determine your Principal and Interest (PI) payments.
The Factors That Affect Your Payment
- Home Price: The total sale price of the property.
- Down Payment: The upfront cash you pay toward the home. A larger down payment reduces the loan amount and often secures a lower interest rate. Standard down payments range from 3% to 20%.
- Interest Rate: The cost of borrowing money, expressed as a percentage. Even a small difference in rates (e.g., 6.5% vs 7.0%) can significantly impact your monthly payment and total interest paid over the life of the loan.
- Loan Term: The duration of the loan. A 30-year term typically offers lower monthly payments but results in higher total interest costs compared to a 15-year term.
How the Math Works
The calculation is based on the following formula:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
Where:
- 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)
Tips for Reducing Your Mortgage Costs
To save money over the life of your loan, consider making bi-weekly payments or paying extra toward the principal when possible. Additionally, improving your credit score before applying can help you qualify for lower interest rates.
function calculateMortgage() {
// 1. Get Input Values
var priceInput = document.getElementById("homePrice");
var downPaymentInput = document.getElementById("downPayment");
var rateInput = document.getElementById("interestRate");
var termInput = document.getElementById("loanTerm");
var price = parseFloat(priceInput.value);
var downPayment = parseFloat(downPaymentInput.value);
var annualRate = parseFloat(rateInput.value);
var years = parseFloat(termInput.value);
// 2. Validation
if (isNaN(price) || isNaN(downPayment) || isNaN(annualRate) || isNaN(years) || price <= 0 || years = price) {
alert("Down payment cannot be equal to or greater than the home price.");
return;
}
// 3. Calculation Logic
var principal = price – downPayment;
var monthlyRate = (annualRate / 100) / 12;
var numberOfPayments = years * 12;
var monthlyPayment = 0;
// Handle zero interest case
if (annualRate === 0) {
monthlyPayment = principal / numberOfPayments;
} else {
// Standard Amortization Formula: M = P[r(1+r)^n]/[(1+r)^n-1]
var numerator = principal * monthlyRate * Math.pow(1 + monthlyRate, numberOfPayments);
var denominator = Math.pow(1 + monthlyRate, numberOfPayments) – 1;
monthlyPayment = numerator / denominator;
}
var totalPayment = monthlyPayment * numberOfPayments;
var totalInterest = totalPayment – principal;
// Calculate Payoff Date
var today = new Date();
var payoffDate = new Date(today.setMonth(today.getMonth() + numberOfPayments));
var options = { month: 'long', year: 'numeric' };
var dateString = payoffDate.toLocaleDateString("en-US", options);
// 4. Output Results
// Helper function for currency formatting
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
document.getElementById("monthlyPayment").innerText = formatter.format(monthlyPayment);
document.getElementById("loanAmountResult").innerText = formatter.format(principal);
document.getElementById("totalInterestResult").innerText = formatter.format(totalInterest);
document.getElementById("totalCostResult").innerText = formatter.format(totalPayment);
document.getElementById("payoffDateResult").innerText = dateString;
// Show results section
document.getElementById("results").style.display = "block";
}