Interest Only Amortization Calculator & Guide | Interest Only Amortization Calculator

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Interest Only Amortization Calculator

Loan Details

Loan Amount ($)

Enter the total amount borrowed.

Annual Interest Rate (%)

Enter the yearly interest rate.

Loan Term (Years)

The total duration of the loan.

Interest-Only Period (Years)

Number of years paying only interest. Must be less than or equal to Loan Term.

Calculation Results

Monthly Interest-Only Payment

$0.00

Total Interest Paid During Interest-Only Period:
$0.00

Principal Balance After Interest-Only Period:
$0.00

Estimated Monthly P&I Payment (After IO Period):
$0.00

Total Interest Paid Over Loan Term:
$0.00

Total Principal Paid Over Loan Term:
$0.00

Total Amount Paid Over Loan Term:
$0.00

Formula Explanation:

The monthly interest-only payment is calculated by dividing the annual interest rate by 12.
The principal balance remains constant during the interest-only period.
After the interest-only period, the loan converts to a standard amortizing loan,
where payments are calculated using the standard loan amortization formula:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1], where M is the monthly payment, P is the remaining principal balance,
i is the monthly interest rate, and n is the number of remaining payments.

Principal vs. Interest Payments Over Time

Amortization Schedule Snippet (First 5 Years)
Year	Starting Balance	Interest Paid	Principal Paid	Ending Balance

Understanding the Interest Only Amortization Calculator

{primary_keyword}: A Comprehensive Guide

What is an Interest Only Amortization Calculator?

An {primary_keyword} is a specialized financial tool designed to help borrowers understand the unique payment structure and long-term implications of an interest-only loan. Unlike traditional loans where each payment includes both principal and interest, an interest-only loan allows borrowers to pay only the interest accrued on the principal balance for a specified period. After this initial interest-only phase, the loan typically converts to a standard amortizing loan, where payments then cover both principal and interest, paying down the loan balance over the remaining term.

This calculator breaks down the financial journey of such a loan. It helps you visualize:

The fixed monthly interest payment during the interest-only period.
The total interest paid and the remaining principal balance at the end of this period.
The significantly higher monthly payments required once the loan converts to principal and interest (P&I).
The total interest and principal paid over the entire life of the loan.

Who should use it?
Anyone considering or currently holding an interest-only mortgage, commercial loan, or construction loan. It’s particularly useful for investors who may use the interest-only period for cash flow flexibility or to capitalize on potential property appreciation before committing to principal repayment.

Common misconceptions:
A frequent misunderstanding is that interest-only loans are always cheaper overall. While the initial payments are lower, the total interest paid over the loan’s life can be substantially higher because the principal balance doesn’t decrease during the interest-only phase. Another misconception is that the loan automatically converts to a standard payment; understanding the terms and the new payment amount is crucial.

{primary_keyword} Formula and Mathematical Explanation

The calculation involves two main phases: the interest-only period and the subsequent P&I amortization period.

Phase 1: Interest-Only Period

During this phase, the borrower pays only the interest accrued on the initial loan amount.

Monthly Interest Payment (M_IO):

M_IO = (Loan Amount * Annual Interest Rate) / 12

Alternatively, using monthly rate (i):

M_IO = Loan Amount * i

Where:

i = Annual Interest Rate / 12

The principal balance (P) remains unchanged throughout this period.

Total Interest Paid During IO Period:

Total Interest_IO = M_IO * (Interest-Only Period in Months)

Principal Balance After IO Period:

Balance_{After IO} = Loan Amount

Phase 2: Principal & Interest (P&I) Amortization Period

After the interest-only period ends, the loan converts to a standard amortizing loan. The remaining principal balance (which is the original loan amount in a pure interest-only scenario) is now paid down over the remaining loan term.

Remaining Loan Term (in months):

n = (Loan Term in Years – Interest-Only Period in Years) * 12

Monthly P&I Payment (M_PI):

This uses the standard loan amortization formula:

M_PI = P_remaining [ i(1 + i)ⁿ ] / [ (1 + i)ⁿ – 1]

Where:

P_remaining = Principal Balance After IO Period
i = Monthly Interest Rate (Annual Interest Rate / 12)
n = Remaining Loan Term in Months

Total Interest Paid Over Loan Term:

Total Interest_Term = (M_IO * Interest-Only Period in Months) + (M_PI * n) – P_remaining

Total Principal Paid Over Loan Term:

Total Principal_Term = P_remaining

Total Amount Paid Over Loan Term:

Total Paid_Term = Total Interest_Term + Total Principal_Term

Variables Table

Variable	Meaning	Unit	Typical Range
Loan Amount (P)	The total sum borrowed.	Currency ($)	$10,000 – $1,000,000+
Annual Interest Rate (AIR)	The yearly cost of borrowing, expressed as a percentage.	%	1% – 15%+
Loan Term (LT)	The total duration of the loan agreement.	Years	5 – 30+ Years
Interest-Only Period (IO)	The duration within the loan term where only interest is paid.	Years	0 – LT Years
Monthly Interest Rate (i)	The interest rate applied per month.	Decimal (AIR / 1200)	0.00083 – 0.125+
Remaining Term (n)	The number of months left to repay the principal after the IO period.	Months	12 – (LT * 12) Months
Monthly Interest-Only Payment (M_IO)	The fixed payment during the IO period.	Currency ($)	Calculated
Monthly P&I Payment (M_PI)	The payment after the IO period, covering principal and interest.	Currency ($)	Calculated

Practical Examples (Real-World Use Cases)

Example 1: Investment Property Purchase

An investor purchases a rental property using an interest-only loan to maximize cash flow during the initial years while hoping for property appreciation.

Loan Amount: $300,000
Annual Interest Rate: 6.0%
Loan Term: 30 Years
Interest-Only Period: 10 Years

Calculations:

Monthly Interest Rate (i) = 6.0% / 12 = 0.5% or 0.005
Monthly Interest-Only Payment: $300,000 * 0.005 = $1,500.00
Total Interest Paid During IO Period (10 years * 12 months/year * $1,500) = $180,000
Principal Balance After IO Period: $300,000
Remaining Term (n) = (30 – 10) years * 12 months/year = 240 months
Estimated Monthly P&I Payment (After IO Period): Using the amortization formula, this calculates to approximately $1,915.75.
Total Interest Paid Over Loan Term: ($180,000) + ($1,915.75 * 240) – $300,000 = $339,780
Total Principal Paid Over Loan Term: $300,000
Total Amount Paid Over Loan Term: $339,780 + $300,000 = $639,780

Financial Interpretation: The investor benefits from lower initial payments ($1,500 vs. $1,915.75), freeing up capital. However, they will pay significantly more interest over the loan’s life ($339,780 vs. $279,780 on a standard loan) and must be prepared for the substantial payment increase after 10 years.

Example 2: Construction Loan Conversion

A developer uses a construction loan that is interest-only during the building phase and converts to a 20-year P&I loan upon completion.

Loan Amount: $500,000
Annual Interest Rate: 7.5%
Loan Term: 25 Years (Total)
Interest-Only Period: 5 Years

Calculations:

Monthly Interest Rate (i) = 7.5% / 12 = 0.625% or 0.00625
Monthly Interest-Only Payment: $500,000 * 0.00625 = $3,125.00
Total Interest Paid During IO Period (5 years * 12 months/year * $3,125) = $187,500
Principal Balance After IO Period: $500,000
Remaining Term (n) = (25 – 5) years * 12 months/year = 240 months
Estimated Monthly P&I Payment (After IO Period): Using the amortization formula, this calculates to approximately $3,355.71.
Total Interest Paid Over Loan Term: ($187,500) + ($3,355.71 * 240) – $500,000 = $497,810.40
Total Principal Paid Over Loan Term: $500,000
Total Amount Paid Over Loan Term: $497,810.40 + $500,000 = $997,810.40

Financial Interpretation: The developer manages cash flow during construction with lower initial payments. The significant increase in monthly payments post-construction ($3,125 to $3,355.71) needs to be factored into the project’s profitability. The total interest paid is substantial, reflecting the longer period the principal remains outstanding. This highlights the importance of a solid exit strategy or refinancing plan.

How to Use This Interest Only Amortization Calculator

Using the {primary_keyword} is straightforward. Follow these steps to get accurate results:

Enter Loan Amount: Input the total principal amount you are borrowing.
Input Annual Interest Rate: Enter the yearly interest rate as a percentage (e.g., 5 for 5%).
Specify Loan Term: Enter the total duration of the loan in years (e.g., 30).
Define Interest-Only Period: Enter the number of years you plan to make only interest payments. This value must be less than or equal to the total Loan Term.
Click ‘Calculate’: The calculator will instantly update with the results.

How to read results:

Monthly Interest-Only Payment: This is the fixed amount you’ll pay each month during the specified interest-only period.
Total Interest Paid During Interest-Only Period: The cumulative interest you’ll pay before principal repayment begins.
Principal Balance After Interest-Only Period: This shows the remaining loan balance when the P&I phase starts (typically the original loan amount for a pure interest-only loan).
Estimated Monthly P&I Payment (After IO Period): This is the crucial figure showing how much your payment will increase once you start repaying the principal.
Total Interest Paid Over Loan Term: The total interest cost for the entire duration of the loan.
Total Principal Paid Over Loan Term: The total amount of the original loan that will be repaid.
Total Amount Paid Over Loan Term: The sum of all principal and interest payments.

Decision-making guidance:
Compare the calculated monthly interest-only payment with your current cash flow. Critically assess if you can afford the projected P&I payment after the interest-only period expires. Consider your long-term financial goals, potential income changes, and the overall cost of interest. This calculator helps quantify the trade-offs between lower initial payments and higher long-term costs.

Key Factors That Affect {primary_keyword} Results

Several variables significantly influence the outcome of an interest-only loan structure. Understanding these is key to making informed financial decisions:

Loan Amount: A larger principal naturally leads to higher interest charges and, consequently, higher monthly payments, both during the interest-only phase and the P&I phase.
Annual Interest Rate: This is perhaps the most impactful factor. Even small increases in the interest rate can dramatically increase the monthly interest cost and the total interest paid over the loan’s life. Higher rates mean more money going towards interest, leaving less for principal repayment in the later stages.
Loan Term: While a longer loan term reduces the monthly P&I payment after the interest-only period, it also extends the time over which interest accrues, potentially increasing the total interest paid significantly.
Interest-Only Period Length: The longer the interest-only period, the more interest you accumulate without reducing the principal. This directly increases the total interest paid over the loan’s life and delays the start of principal reduction.
Fees and Closing Costs: Many loans, especially commercial or specialized ones, come with origination fees, appraisal fees, and other closing costs. These add to the overall expense of the loan and should be factored into the total cost of borrowing, even if not directly part of the amortization calculation.
Future Interest Rate Changes (for variable rates): If the loan has a variable interest rate, future rate increases can substantially raise the monthly interest-only payment and the subsequent P&I payment, making long-term budgeting challenging. This introduces significant risk.
Inflation and Opportunity Cost: While lower initial payments might seem attractive, high inflation can erode the purchasing power of money. The funds saved on principal payments could potentially be invested elsewhere, but this carries its own risks and requires careful consideration of returns versus loan interest rates.
Tax Implications: Interest paid on certain types of loans (like investment properties) may be tax-deductible. Understanding these tax benefits can alter the net cost of the loan. Conversely, capital gains taxes on appreciation might affect the overall profitability of an investment strategy using interest-only loans.

Frequently Asked Questions (FAQ)

Q1: What is the main advantage of an interest-only loan?

A1: The primary advantage is lower initial monthly payments, which can improve cash flow, especially for investors or during periods of expected income growth. It allows borrowers to potentially invest elsewhere or manage finances more flexibly during the interest-only period.

Q2: What is the biggest risk of an interest-only loan?

A2: The biggest risk is that the principal balance does not decrease during the interest-only period. This means you pay significantly more interest over the life of the loan compared to a traditional amortizing loan. Additionally, borrowers must be prepared for the substantial increase in payments when the loan converts to P&I.

Q3: Can I pay extra principal during the interest-only period?

A3: Yes, most interest-only loans allow you to make additional principal payments. Doing so can reduce the total interest paid over the loan’s life and shorten the repayment term, effectively converting it into a standard amortizing loan sooner. Always check your loan agreement for any prepayment penalties.

Q4: What happens if I can’t afford the P&I payments after the interest-only period?

A4: If you cannot afford the increased payments, you may face default. Options could include selling the property, seeking a loan modification (though often difficult), or refinancing the loan. It’s crucial to plan for this payment increase well in advance.

Q5: Are interest-only loans only for mortgages?

A5: No, interest-only loans are common for various financial products, including commercial real estate, construction loans, and sometimes auto loans or personal loans, although less frequently for the latter.

Q6: How does a variable interest rate affect an interest-only loan?

A6: A variable rate introduces uncertainty. Your monthly interest-only payment could increase if market rates rise, and the subsequent P&I payment would also be higher than initially projected. This adds significant risk to financial planning.

Q7: Is an interest-only loan a good idea for a primary residence?

A7: Generally, it’s less common and often less advisable for primary residences compared to investment properties. The primary benefit (cash flow flexibility) is less critical for homeowners, while the risk of higher total interest paid and the payment shock are significant drawbacks. Traditional amortizing loans are usually preferred for owner-occupied homes.

Q8: How does the {primary_keyword} calculator handle different loan terms?

A8: The calculator dynamically adjusts calculations based on the total loan term and the specified interest-only period. It calculates the remaining term for the P&I phase and uses that in the amortization formula to determine the future payments and total interest.

Related Tools and Internal Resources

var chartInstance = null; // Global variable to hold chart instance

function validateInput(id, min, max, errorId, errorMessageEmpty, errorMessageRange) {
var input = document.getElementById(id);
var value = parseFloat(input.value);
var errorDiv = document.getElementById(errorId);
errorDiv.textContent = ”; // Clear previous error

if (isNaN(value) || input.value.trim() === ”) {
errorDiv.textContent = errorMessageEmpty;
return false;
}
if (value max)) {
errorDiv.textContent = errorMessageRange;
return false;
}
return true;
}

function calculateAmortization() {
// Clear previous errors
document.getElementById(‘loanAmountError’).textContent = ”;
document.getElementById(‘annualInterestRateError’).textContent = ”;
document.getElementById(‘loanTermYearsError’).textContent = ”;
document.getElementById(‘interestOnlyPeriodYearsError’).textContent = ”;

// Validate inputs
var isValidLoanAmount = validateInput(‘loanAmount’, 0, null, ‘loanAmountError’, ‘Loan amount cannot be empty.’, ‘Loan amount must be positive.’);
var isValidAnnualInterestRate = validateInput(‘annualInterestRate’, 0, 100, ‘annualInterestRateError’, ‘Interest rate cannot be empty.’, ‘Interest rate must be between 0% and 100%.’);
var isValidLoanTermYears = validateInput(‘loanTermYears’, 1, null, ‘loanTermYearsError’, ‘Loan term cannot be empty.’, ‘Loan term must be at least 1 year.’);
var isValidInterestOnlyPeriodYears = validateInput(‘interestOnlyPeriodYears’, 0, null, ‘interestOnlyPeriodYearsError’, ‘Interest-only period cannot be empty.’, ‘Interest-only period must be non-negative.’);

var loanTermYears = parseFloat(document.getElementById(‘loanTermYears’).value);
var interestOnlyPeriodYears = parseFloat(document.getElementById(‘interestOnlyPeriodYears’).value);

if (interestOnlyPeriodYears > loanTermYears) {
document.getElementById(‘interestOnlyPeriodYearsError’).textContent = ‘Interest-only period cannot exceed loan term.’;
isValidInterestOnlyPeriodYears = false;
}

if (!isValidLoanAmount || !isValidAnnualInterestRate || !isValidLoanTermYears || !isValidInterestOnlyPeriodYears) {
document.getElementById(‘results’).style.display = ‘none’;
return;
}

var loanAmount = parseFloat(document.getElementById(‘loanAmount’).value);
var annualInterestRate = parseFloat(document.getElementById(‘annualInterestRate’).value);
var loanTermYears = parseFloat(document.getElementById(‘loanTermYears’).value);
var interestOnlyPeriodYears = parseFloat(document.getElementById(‘interestOnlyPeriodYears’).value);

var monthlyInterestRate = annualInterestRate / 100 / 12;
var numberOfMonths = loanTermYears * 12;
var interestOnlyPeriodMonths = interestOnlyPeriodYears * 12;
var remainingMonths = numberOfMonths – interestOnlyPeriodMonths;

// Calculate Monthly Interest-Only Payment
var monthlyInterestOnlyPayment = loanAmount * monthlyInterestRate;

// Calculate Total Interest Paid During IO Period
var totalInterestDuringIO = monthlyInterestOnlyPayment * interestOnlyPeriodMonths;

// Principal Balance After IO Period remains the same as loanAmount for pure IO
var balanceAfterIO = loanAmount;

// Calculate Monthly P&I Payment after IO period
var monthlyPIPayment = 0;
if (remainingMonths > 0) {
monthlyPIPayment = loanAmount * (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, remainingMonths)) / (Math.pow(1 + monthlyInterestRate, remainingMonths) – 1);
} else {
// If IO period is the entire loan term, P&I payment is 0
monthlyPIPayment = 0;
}

// Calculate Total Interest Paid Over Loan Term
var totalInterestOverTerm = totalInterestDuringIO + (monthlyPIPayment * remainingMonths) – loanAmount;
if (isNaN(totalInterestOverTerm) || totalInterestOverTerm 0 ? ‘$’ + monthlyPIPayment.toFixed(2) : ‘N/A’;
document.getElementById(‘totalInterestOverTerm’).textContent = ‘$’ + totalInterestOverTerm.toFixed(2);
document.getElementById(‘totalPrincipalPaid’).textContent = ‘$’ + totalPrincipalPaid.toFixed(2);
document.getElementById(‘totalAmountPaid’).textContent = ‘$’ + totalAmountPaid.toFixed(2);

document.getElementById(‘results’).style.display = ‘block’;

// Update Chart
updateChart(loanAmount, monthlyInterestOnlyPayment, monthlyPIPayment, interestOnlyPeriodMonths, remainingMonths, monthlyInterestRate);

// Update Table
updateTable(loanAmount, monthlyInterestOnlyPayment, monthlyPIPayment, interestOnlyPeriodMonths, remainingMonths, monthlyInterestRate);
}

function updateChart(loanAmount, monthlyInterestOnlyPayment, monthlyPIPayment, interestOnlyPeriodMonths, remainingMonths, monthlyInterestRate) {
var ctx = document.getElementById(‘amortizationChart’).getContext(‘2d’);

// Destroy previous chart instance if it exists
if (chartInstance) {
chartInstance.destroy();
}

var labels = [];
var principalData = [];
var interestData = [];
var currentBalance = loanAmount;
var totalInterestAccrued = 0;

// Interest-Only Period Data
for (var i = 0; i < interestOnlyPeriodMonths; i++) {
labels.push('Year ' + Math.floor(i / 12) + ' Month ' + (i % 12 + 1));
principalData.push(loanAmount); // Principal remains constant
interestData.push(monthlyInterestOnlyPayment);
totalInterestAccrued += monthlyInterestOnlyPayment;
}

// P&I Period Data
var payment = monthlyPIPayment;
for (var i = 0; i maxPoints) {
var step = Math.ceil(labels.length / maxPoints);
var simplifiedLabels = [];
var simplifiedPrincipal = [];
var simplifiedInterest = [];
for (var i = 0; i 0 ? Math.ceil(interestOnlyPeriodMonths / 12) : 0);
if (limitYears === 0 && loanAmount > 0) limitYears = Math.min(5, Math.ceil(loanAmount / (monthlyPIPayment > 0 ? monthlyPIPayment * 12 : 1))); // If no IO period, show first 5 years of P&I

for (var i = 0; i < limitYears * 12; i++) {
var row = tableBody.insertRow();
var startingBalance = currentBalance;
var interestPayment = 0;
var principalPayment = 0;

if (i 0) {
interestPayment = currentBalance * monthlyInterestRate;
principalPayment = monthlyPIPayment – interestPayment;
currentBalance -= principalPayment;
} else {
// Should not happen if limitYears is calculated correctly, but as a fallback
break;
}

// Ensure balance doesn’t go negative due to floating point errors
if (currentBalance < 0.01) currentBalance = 0;

interestPaidTotal += interestPayment;
principalPaidTotal += principalPayment;

var displayYear = Math.floor(i / 12);
var displayMonth = i % 12;

// Only add row if it's within the limit years or if it's the last row of the IO period
if (displayYear 0)) {
row.insertCell(0).textContent = displayYear;
row.insertCell(1).textContent = startingBalance.toLocaleString(‘en-US’, { style: ‘currency’, currency: ‘USD’ });
row.insertCell(2).textContent = interestPayment.toLocaleString(‘en-US’, { style: ‘currency’, currency: ‘USD’ });
row.insertCell(3).textContent = principalPayment.toLocaleString(‘en-US’, { style: ‘currency’, currency: ‘USD’ });
row.insertCell(4).textContent = currentBalance.toLocaleString(‘en-US’, { style: ‘currency’, currency: ‘USD’ });
}

// Break if we’ve processed all months needed for the table
if (i >= interestOnlyPeriodMonths && currentBalance === 0) break;
}
// If the IO period extends beyond 5 years, ensure the last row of the IO period is shown
if (interestOnlyPeriodMonths > 0 && interestOnlyPeriodMonths / 12 >= limitYears && tableBody.rows.length > 0) {
var lastRowIndex = tableBody.rows.length -1;
var lastRowYear = parseInt(tableBody.rows[lastRowIndex].cells[0].textContent);
if (lastRowYear < Math.floor(interestOnlyPeriodMonths / 12)) {
// Add the last row of the IO period if it wasn't included
var row = tableBody.insertRow(lastRowIndex + 1); // Insert after the last row shown
var startingBalance = loanAmount; // Balance at start of IO period
var interestPayment = monthlyInterestOnlyPayment;
var principalPayment = 0;
var displayYear = Math.floor(interestOnlyPeriodMonths / 12);
var displayMonth = (interestOnlyPeriodMonths % 12);

row.insertCell(0).textContent = displayYear;
row.insertCell(1).textContent = startingBalance.toLocaleString('en-US', { style: 'currency', currency: 'USD' });
row.insertCell(2).textContent = interestPayment.toLocaleString('en-US', { style: 'currency', currency: 'USD' });
row.insertCell(3).textContent = principalPayment.toLocaleString('en-US', { style: 'currency', currency: 'USD' });
row.insertCell(4).textContent = loanAmount.toLocaleString('en-US', { style: 'currency', currency: 'USD' }); // Balance remains same
}
}
}

function resetCalculator() {
document.getElementById('loanAmount').value = '200000';
document.getElementById('annualInterestRate').value = '5';
document.getElementById('loanTermYears').value = '30';
document.getElementById('interestOnlyPeriodYears').value = '10';

// Clear errors
document.getElementById('loanAmountError').textContent = '';
document.getElementById('annualInterestRateError').textContent = '';
document.getElementById('loanTermYearsError').textContent = '';
document.getElementById('interestOnlyPeriodYearsError').textContent = '';

// Clear results and hide
document.getElementById('results').style.display = 'none';
document.getElementById('monthlyInterestOnlyPayment').textContent = '$0.00';
document.getElementById('totalInterestDuringIO').textContent = '$0.00';
document.getElementById('balanceAfterIO').textContent = '$0.00';
document.getElementById('monthlyPIPayment').textContent = '$0.00';
document.getElementById('totalInterestOverTerm').textContent = '$0.00';
document.getElementById('totalPrincipalPaid').textContent = '$0.00';
document.getElementById('totalAmountPaid').textContent = '$0.00';

// Clear chart
var ctx = document.getElementById('amortizationChart').getContext('2d');
if (chartInstance) {
chartInstance.destroy();
chartInstance = null;
}
ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height); // Clear canvas

// Clear table
document.getElementById('amortizationTableBody').innerHTML = '';
}

function copyResults() {
var resultsText = "Interest Only Amortization Calculator Results:\n\n";
resultsText += "Key Assumptions:\n";
resultsText += "- Loan Amount: $" + document.getElementById('loanAmount').value + "\n";
resultsText += "- Annual Interest Rate: " + document.getElementById('annualInterestRate').value + "%\n";
resultsText += "- Loan Term: " + document.getElementById('loanTermYears').value + " years\n";
resultsText += "- Interest-Only Period: " + document.getElementById('interestOnlyPeriodYears').value + " years\n\n";

resultsText += "Primary Result:\n";
resultsText += "- Monthly Interest-Only Payment: " + document.getElementById('monthlyInterestOnlyPayment').textContent + "\n\n";

resultsText += "Intermediate & Summary Values:\n";
resultsText += "- Total Interest Paid During Interest-Only Period: " + document.getElementById('totalInterestDuringIO').textContent + "\n";
resultsText += "- Principal Balance After Interest-Only Period: " + document.getElementById('balanceAfterIO').textContent + "\n";
resultsText += "- Estimated Monthly P&I Payment (After IO Period): " + document.getElementById('monthlyPIPayment').textContent + "\n";
resultsText += "- Total Interest Paid Over Loan Term: " + document.getElementById('totalInterestOverTerm').textContent + "\n";
resultsText += "- Total Principal Paid Over Loan Term: " + document.getElementById('totalPrincipalPaid').textContent + "\n";
resultsText += "- Total Amount Paid Over Loan Term: " + document.getElementById('totalAmountPaid').textContent + "\n";

// Use a temporary textarea to copy text
var textArea = document.createElement("textarea");
textArea.value = resultsText;
textArea.style.position = "fixed"; // Avoid scrolling to bottom of page in MS Edge.
textArea.style.top = 0;
textArea.style.left = 0;
textArea.style.width = '2em';
textArea.style.height = '2em';
textArea.style.padding = '0';
textArea.style.border = 'none';
textArea.style.outline = 'none';
textArea.style.boxShadow = 'none';
document.body.appendChild(textArea);
textArea.focus();
textArea.select();

try {
var successful = document.execCommand('copy');
var msg = successful ? 'Results copied successfully!' : 'Failed to copy results.';
console.log(msg);
// Optionally show a temporary message to the user
var copyButton = document.querySelector('.btn-copy');
var originalText = copyButton.textContent;
copyButton.textContent = 'Copied!';
setTimeout(function() {
copyButton.textContent = originalText;
}, 2000);
} catch (err) {
console.log('Oops, unable to copy');
}

document.body.removeChild(textArea);
}

// Initial calculation on page load if values are present
document.addEventListener('DOMContentLoaded', function() {
calculateAmortization();
});