.mp-calculator-container {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 20px auto;
padding: 20px;
background: #f9f9f9;
border: 1px solid #e0e0e0;
border-radius: 8px;
}
.mp-calc-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
}
@media (max-width: 600px) {
.mp-calc-grid {
grid-template-columns: 1fr;
}
}
.mp-input-group {
margin-bottom: 15px;
}
.mp-input-group label {
display: block;
font-weight: 600;
margin-bottom: 5px;
color: #333;
}
.mp-input-group input {
width: 100%;
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.mp-input-group input:focus {
border-color: #0073aa;
outline: none;
}
.mp-btn {
grid-column: 1 / -1;
background-color: #0073aa;
color: white;
border: none;
padding: 15px;
font-size: 18px;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
transition: background 0.3s;
width: 100%;
}
.mp-btn:hover {
background-color: #005177;
}
.mp-results {
grid-column: 1 / -1;
background: #fff;
border: 1px solid #ddd;
padding: 20px;
border-radius: 4px;
margin-top: 20px;
display: none;
}
.mp-results h3 {
margin-top: 0;
color: #2c3e50;
border-bottom: 2px solid #0073aa;
padding-bottom: 10px;
}
.mp-stat-row {
display: flex;
justify-content: space-between;
padding: 10px 0;
border-bottom: 1px solid #eee;
}
.mp-stat-row:last-child {
border-bottom: none;
}
.mp-stat-label {
color: #555;
}
.mp-stat-value {
font-weight: bold;
color: #000;
}
.mp-highlight {
color: #27ae60;
}
.mp-article {
max-width: 800px;
margin: 40px auto;
line-height: 1.6;
color: #333;
}
.mp-article h2 {
color: #2c3e50;
margin-top: 30px;
}
.mp-article ul {
margin-bottom: 20px;
}
.mp-article li {
margin-bottom: 10px;
}
function calculateMortgagePayoff() {
// 1. Get Inputs
var balance = parseFloat(document.getElementById('currentBalance').value);
var rate = parseFloat(document.getElementById('interestRate').value);
var years = parseFloat(document.getElementById('remainingTerm').value);
var extra = parseFloat(document.getElementById('extraPayment').value);
// 2. Validate Inputs
if (isNaN(balance) || balance <= 0 || isNaN(rate) || rate < 0 || isNaN(years) || years <= 0) {
alert("Please enter valid positive numbers for Balance, Rate, and Term.");
return;
}
if (isNaN(extra) || extra 0) {
monthsPassed++;
var interestForMonth = currentBal * monthlyRate;
var principalForMonth = actualPayment – interestForMonth;
// Handle final month
if (currentBal 1000) break;
}
// 6. Calculate Savings
var interestSavedVal = totalInterestOrig – totalInterestNew;
if (interestSavedVal 0) timeSavedString += yearsSaved + " Years ";
if (remMonthsSaved > 0) timeSavedString += remMonthsSaved + " Months";
if (timeSavedString === "") timeSavedString = "0 Months";
document.getElementById('timeSaved').innerText = timeSavedString;
// Format Currency
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
});
document.getElementById('interestSaved').innerText = formatter.format(interestSavedVal);
// Show Results
document.getElementById('mpResult').style.display = 'block';
}
Understanding Your Mortgage Payoff Strategy
Paying off a mortgage early is one of the most effective ways to secure your financial future. By applying extra payments directly to your principal balance, you drastically reduce the amount of interest calculated over the life of the loan. This calculator demonstrates exactly how small additional contributions can shave years off your mortgage term.
How Mortgage Amortization Works
In the early years of a standard mortgage, the majority of your monthly payment goes toward interest, with very little reducing the principal. This is known as amortization. For example, on a new $300,000 loan at 6%, your first payment might be $1,800, but roughly $1,500 of that is just interest.
By making an extra principal payment, you skip ahead in the amortization schedule. You aren't just paying down debt; you are eliminating future interest charges on that specific amount of capital.
Benefits of Using This Calculator
- Visualize Savings: See exactly how much interest you save by adding $50, $100, or $500 to your monthly payment.
- Timeline Adjustment: Determine precisely when you will be debt-free based on your extra contributions.
- Budget Planning: Test different scenarios to find an extra payment amount that fits your current budget without overextending.
The Mathematical Formula
This tool uses the standard amortization formula to calculate your base monthly payment:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
Where M is the total monthly payment, P is the principal loan amount, i is the monthly interest rate, and n is the number of months required to repay the loan. The calculator then iterates through the loan schedule, subtracting the extra payment from the principal every month to calculate the new payoff date and total interest reduction.
Frequently Asked Questions
Does my lender allow extra payments?
Most modern lenders allow extra payments without penalty, but it is crucial to specify that the extra funds should be applied to the principal, not toward future interest payments.
Is it better to invest or pay off the mortgage?
This depends on your interest rate versus potential investment returns. If your mortgage rate is high (e.g., 6-7%), paying it off is a guaranteed return on investment. If your rate is low (e.g., 3%), investing might yield higher returns. Use the "Total Interest Saved" metric from this calculator to compare against potential investment gains.