Extra Payments Calculator

Extra Payments Calculator: Pay Down Loans Faster :root { –primary-color: #004a99; –success-color: #28a745; –background-color: #f8f9fa; –text-color: #333; –border-color: #ddd; –card-background: #fff; –shadow: 0 4px 8px rgba(0,0,0,0.1); } body { font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif; background-color: var(–background-color); color: var(–text-color); margin: 0; padding: 20px; line-height: 1.6; } .container { max-width: 960px; margin: 20px auto; background-color: var(–card-background); padding: 30px; border-radius: 8px; box-shadow: var(–shadow); border: 1px solid var(–border-color); } h1, h2, h3 { color: var(–primary-color); text-align: center; margin-bottom: 20px; } h1 { font-size: 2.2em; } h2 { font-size: 1.8em; margin-top: 40px; } h3 { font-size: 1.4em; margin-top: 30px; } .loan-calc-container { background-color: var(–card-background); padding: 25px; border-radius: 8px; box-shadow: var(–shadow); border: 1px solid var(–border-color); margin-bottom: 30px; } .input-group { margin-bottom: 20px; } .input-group label { display: block; margin-bottom: 8px; font-weight: bold; color: var(–primary-color); } .input-group input[type="number"], .input-group input[type="text"], .input-group select { width: calc(100% – 20px); padding: 12px 10px; border: 1px solid var(–border-color); border-radius: 5px; font-size: 1em; box-sizing: border-box; } .input-group input[type="number"]:focus, .input-group input[type="text"]:focus, .input-group select:focus { outline: none; border-color: var(–primary-color); box-shadow: 0 0 0 2px rgba(0, 74, 153, 0.2); } .input-group .helper-text { font-size: 0.85em; color: #666; margin-top: 5px; display: block; } .input-group .error-message { font-size: 0.8em; color: red; margin-top: 5px; display: block; min-height: 1.2em; } .button-group { display: flex; justify-content: space-between; margin-top: 25px; } button { padding: 12px 20px; background-color: var(–primary-color); color: white; border: none; border-radius: 5px; font-size: 1em; cursor: pointer; transition: background-color 0.3s ease; font-weight: bold; } button:hover { background-color: #003366; } button#resetBtn { background-color: #6c757d; } button#resetBtn:hover { background-color: #5a6268; } .results-container { margin-top: 30px; padding: 25px; background-color: var(–primary-color); color: white; border-radius: 8px; box-shadow: var(–shadow); text-align: center; } .results-container h2 { color: white; margin-bottom: 15px; } .primary-result { font-size: 2.5em; font-weight: bold; margin: 15px 0; display: block; padding: 10px; background-color: var(–success-color); border-radius: 5px; } .intermediate-results div { margin-bottom: 10px; font-size: 1.1em; } .intermediate-results span { font-weight: bold; } .formula-explanation { font-size: 0.9em; color: rgba(255,255,255,0.9); margin-top: 15px; } .copy-button { background-color: #17a2b8; margin-top: 15px; } .copy-button:hover { background-color: #117a8b; } table { width: 100%; border-collapse: collapse; margin-top: 30px; box-shadow: var(–shadow); } caption { font-size: 1.1em; font-weight: bold; color: var(–primary-color); margin-bottom: 10px; text-align: left; } th, td { border: 1px solid var(–border-color); padding: 12px; text-align: right; } th { background-color: var(–primary-color); color: white; font-weight: bold; } td:first-child { text-align: left; } tr:nth-child(even) { background-color: #f2f2f2; } #amortizationChart { display: block; margin: 30px auto; border: 1px solid var(–border-color); border-radius: 5px; box-shadow: var(–shadow); } .chart-container { text-align: center; margin-top: 30px; } .chart-container p { font-style: italic; color: #666; margin-bottom: 10px; } .article-section { margin-top: 40px; padding-top: 20px; border-top: 1px solid var(–border-color); } .article-section h2 { text-align: left; } .article-section h3 { text-align: left; margin-top: 25px; } .article-section p { margin-bottom: 15px; } .article-section ul, .article-section ol { margin-left: 20px; margin-bottom: 15px; } .article-section li { margin-bottom: 8px; } .article-section strong { color: var(–primary-color); } .internal-links-list { list-style: none; padding: 0; } .internal-links-list li { margin-bottom: 15px; } .internal-links-list a { font-weight: bold; color: var(–primary-color); text-decoration: none; } .internal-links-list a:hover { text-decoration: underline; } .internal-links-list p { font-size: 0.9em; color: #555; margin-top: 5px; } @media (max-width: 768px) { .container { padding: 20px; } h1 { font-size: 1.8em; } h2 { font-size: 1.5em; } h3 { font-size: 1.2em; } .button-group { flex-direction: column; gap: 10px; } .button-group button { width: 100%; } .results-container { padding: 20px; } .primary-result { font-size: 2em; } th, td { padding: 8px; font-size: 0.9em; } }

Extra Payments Calculator

See how making extra payments can significantly reduce your loan term and total interest paid. Calculate the impact of additional contributions on your mortgage, auto loan, or any other installment loan.

Enter the remaining balance of your loan.
Enter the annual interest rate without the '%' sign.
Enter the number of months left on your loan.
Enter the additional amount you plan to pay each month.

Your Results

Original Total Interest: $0
Original Total Cost: $0
New Total Interest: $0
Interest Saved: $0
Time Saved: 0 months
$0
Calculations are based on an amortization schedule, applying extra payments to the principal. Results are estimates and may vary.

Loan Amortization Comparison

Amortization Schedule – With Extra Payments
Month Starting Balance Payment Principal Paid Interest Paid Ending Balance
Enter loan details and click "Calculate" to see the schedule.

What is an Extra Payments Calculator?

An extra payments calculator is a powerful financial tool designed to illustrate the impact of making payments beyond your scheduled loan installments. It helps individuals understand how adding even a small amount regularly to their loan payments can lead to significant savings in interest and a faster payoff timeline. This calculator is particularly useful for anyone looking to accelerate their debt repayment, whether it's for a mortgage, auto loan, student loan, or personal loan. By inputting your current loan details, such as the principal balance, interest rate, remaining term, and the amount you plan to pay extra each month, the calculator projects your new loan payoff date and the total interest you will save over the life of the loan. Understanding these potential benefits can be a strong motivator for disciplined financial management. It demystifies the complex mathematics of loan amortization and provides clear, actionable insights into debt reduction strategies. Many people have common misconceptions about the power of extra payments; they might underestimate the cumulative effect of small additional amounts or overestimate the complexity of implementing such a strategy. This tool aims to provide clarity and empower users with knowledge.

Who Should Use an Extra Payments Calculator?

Virtually anyone with an outstanding loan can benefit from using an extra payments calculator. This includes:

  • Homeowners: To see how extra mortgage payments can build equity faster and save tens or even hundreds of thousands of dollars in interest over 30 years.
  • Auto Loan Borrowers: To pay off their car loans sooner and reduce the total interest paid, freeing up monthly cash flow.
  • Student Loan Debtors: To tackle the often-substantial burden of student loans more aggressively, potentially saving significant amounts over the long term.
  • Individuals with Personal Loans: To become debt-free faster and improve their financial standing.
  • Budget-Conscious Individuals: To visualize the financial benefits of allocating extra funds towards debt repayment rather than other expenses.
  • Financial Planners and Advisors: To demonstrate debt reduction strategies to clients.

Common Misconceptions about Extra Payments

Several myths surround the strategy of making extra loan payments:

  • "It doesn't make that much difference": Even small, consistent extra payments can compound significantly over time due to the principles of amortization, saving substantial interest.
  • "It's too complicated to track": Modern tools and clear communication with lenders make it straightforward to ensure extra payments are applied to the principal.
  • "I need to pay a huge amount extra": While larger payments have a greater impact, even modest additional amounts yield considerable benefits.
  • "All extra payments go to interest": Lenders are typically required to apply extra payments directly to the principal balance, reducing the amount on which future interest is calculated. Always confirm this with your lender.

Using the extra payments calculator helps to debunk these myths by showing tangible results.

Extra Payments Calculator Formula and Mathematical Explanation

The extra payments calculator essentially simulates an amortization schedule. It recalculates the loan's payoff timeline and total interest paid by incorporating the additional monthly payment. The core logic involves repeatedly calculating the monthly interest, applying the total payment (scheduled + extra) to reduce the principal, and updating the remaining balance until it reaches zero.

The Amortization Process

For each payment period (typically monthly), the following steps occur:

  1. Calculate Monthly Interest: The interest accrued for the current period is calculated based on the outstanding principal balance. The formula is: Monthly Interest = (Remaining Principal Balance * Annual Interest Rate) / 12
  2. Calculate Total Payment: This is the sum of the scheduled principal and interest payment plus the extra monthly payment. Total Payment = Scheduled P&I Payment + Extra Monthly Payment
  3. Apply Payment to Principal: The portion of the total payment that goes towards reducing the principal is determined. First, the interest accrued for the month is paid off. The remainder of the total payment is then applied to the principal. Principal Paid = Total Payment - Monthly Interest
  4. Update Remaining Balance: The principal paid is subtracted from the current outstanding balance. New Remaining Balance = Remaining Principal Balance - Principal Paid
  5. Repeat: These steps are repeated for each subsequent month until the remaining balance is zero or less.

The calculator determines the original loan's total interest and term, then simulates the process with the added extra payment to find the new total interest, savings, and payoff time. The result for "Time Saved" is the difference between the original term and the new, shortened term.

Variables Involved

Here's a breakdown of the key variables used in the calculations:

Variable Meaning Unit Typical Range
P (Loan Amount) Initial principal balance of the loan. Currency ($) $1,000 – $1,000,000+
r (Annual Interest Rate) The yearly interest rate charged by the lender. Percentage (%) 1% – 30%+
n (Original Term) The original total number of payment periods (months). Months 12 – 360+
M (Scheduled Monthly Payment) The fixed monthly payment calculated using the loan amortization formula: M = P [ r(1 + r)^n ] / [ (1 + r)^n – 1] where 'r' is the monthly interest rate (Annual Rate / 12). Currency ($) Varies based on P, r, n
E (Extra Monthly Payment) The additional amount paid each month towards the principal. Currency ($) $10 – $1,000+
Total Interest Paid Sum of all interest paid over the life of the loan. Currency ($) Varies
Total Cost Sum of all payments made (Principal + Total Interest). Currency ($) Varies
New Term The shortened number of months to pay off the loan with extra payments. Months Less than 'n'

The extra payments calculator performs these calculations iteratively to provide accurate results.

Practical Examples (Real-World Use Cases)

Let's explore how the extra payments calculator can be used with realistic scenarios:

Example 1: Accelerating Mortgage Payoff

Scenario: Sarah and John are 5 years into their 30-year mortgage. They have a remaining balance of $300,000 and a fixed annual interest rate of 4.5%. Their scheduled monthly payment (principal and interest) is $1,520. They decide they can comfortably afford to add an extra $200 per month towards their mortgage.

Inputs for the Calculator:

  • Current Loan Balance: $300,000
  • Annual Interest Rate: 4.5%
  • Remaining Term: 25 years * 12 months/year = 300 months
  • Extra Monthly Payment: $200

Calculator Output (Estimated):

  • Original Total Interest Paid: ~$256,500
  • Original Total Cost: ~$556,500
  • New Total Interest Paid: ~$195,800
  • Interest Saved: ~$60,700
  • Time Saved: ~4 years and 5 months
  • New Payoff Time: Approximately 20 years and 7 months

Financial Interpretation: By paying an extra $200 per month, Sarah and John will pay off their mortgage over 55 months sooner and save over $60,000 in interest. This is a significant financial gain achieved through consistent, disciplined extra payments.

Example 2: Paying Off a Car Loan Early

Scenario: Michael recently bought a car and financed $25,000 at an annual interest rate of 6%. The loan term is 5 years (60 months), with a monthly payment of $483. He received a bonus and wants to see how paying an extra $150 per month would affect his loan.

Inputs for the Calculator:

  • Current Loan Balance: $25,000
  • Annual Interest Rate: 6%
  • Remaining Term: 60 months
  • Extra Monthly Payment: $150

Calculator Output (Estimated):

  • Original Total Interest Paid: ~$4,000
  • Original Total Cost: ~$29,000
  • New Total Interest Paid: ~$2,100
  • Interest Saved: ~$1,900
  • Time Saved: ~1 year and 7 months
  • New Payoff Time: Approximately 3 years and 5 months

Financial Interpretation: Michael's extra $150 monthly payment not only saves him nearly $2,000 in interest but also allows him to be car-payment free almost two years earlier. This frees up significant cash flow sooner, which he could then allocate to other financial goals, like saving or investing.

These examples demonstrate the profound effect consistent additional payments can have on reducing debt and saving money, showcasing the utility of the extra payments calculator.

How to Use This Extra Payments Calculator

Using our extra payments calculator is simple and intuitive. Follow these steps to understand your debt reduction potential:

  1. Enter Your Loan Balance: In the "Current Loan Balance ($)" field, input the exact amount you currently owe on your loan.
  2. Input Your Interest Rate: Enter your loan's annual interest rate in the "Annual Interest Rate (%)" field. Make sure to enter it as a whole number (e.g., 4.5 for 4.5%).
  3. Specify Remaining Term: In the "Remaining Term (Months)" field, enter the total number of months left until your loan is fully paid off based on your current payment schedule.
  4. Determine Extra Payment Amount: In the "Extra Monthly Payment ($)" field, enter the additional amount you are willing and able to pay each month. Even a small amount can make a difference!
  5. Click "Calculate": Once all fields are populated, click the "Calculate" button.

Reading the Results

After clicking "Calculate," you will see several key pieces of information:

  • Primary Highlighted Result: This large, prominent number shows your estimated Total Interest Saved by making extra payments.
  • Intermediate Values:
    • Original Total Interest: The total interest you would pay if you only made scheduled payments.
    • Original Total Cost: The total amount (principal + interest) you would pay without extra payments.
    • New Total Interest: The total interest you will pay with the added extra payments.
    • Interest Saved: The difference between the original total interest and the new total interest (this is your primary result).
    • Time Saved: How many months (and potentially years) you will shave off your loan term.
  • Amortization Table: A detailed month-by-month breakdown showing how each payment is allocated to principal and interest, and how the balance decreases over time with your extra payments applied.
  • Loan Amortization Comparison Chart: A visual representation comparing the loan's progress with and without extra payments, highlighting the accelerated principal reduction.

Decision-Making Guidance

Use the results to make informed financial decisions:

  • Affordability: Assess if the "Extra Monthly Payment" you entered is genuinely sustainable within your budget. Aim for amounts that provide significant savings without causing financial strain.
  • Goal Setting: The "Time Saved" metric can help you set realistic goals for becoming debt-free.
  • Prioritization: If you have multiple debts, use this calculator (and others like it) to prioritize which loans to tackle first based on interest saved and payoff speed. Consider prioritizing high-interest debt. You can learn more about debt consolidation strategies.
  • Lender Communication: Remember to confirm with your lender that extra payments are applied directly to the principal. Most lenders allow this, but it's crucial to verify.

The extra payments calculator is a tool for empowerment, providing the data you need to take control of your debt.

Key Factors That Affect Extra Payments Calculator Results

While the extra payments calculator provides a clear projection, several underlying factors influence the accuracy and magnitude of the results:

  1. Interest Rate (r): This is arguably the most significant factor. Higher interest rates mean more of your regular payment goes towards interest. Therefore, making extra payments on high-interest loans yields much greater savings compared to low-interest loans. The calculator highlights this by showing a larger "Interest Saved" figure for loans with higher rates.
  2. Loan Term (n): Longer loan terms offer more opportunities for extra payments to compound their effect. Paying an extra $100 on a 30-year mortgage will save far more in interest over its lifetime than paying an extra $100 on a 3-year car loan, simply because there are many more months for the extra payments to chip away at the principal and reduce future interest accrual.
  3. Loan Amount (P): While the rate and term are crucial, the initial loan amount sets the scale. Larger loans naturally have higher interest costs, meaning extra payments can lead to more substantial dollar savings, even if the percentage or time savings are similar to a smaller loan.
  4. Frequency and Consistency of Extra Payments: The calculator assumes consistent, regular extra payments applied monthly. Irregular extra payments or missing payments will alter the results. The power lies in consistent application.
  5. Loan Type and Structure: While the calculator works for most standard amortizing loans (mortgages, auto, personal), some loans have specific prepayment penalties or unique structures. Always check your loan agreement. This calculator assumes no prepayment penalties.
  6. Inflation and Opportunity Cost: While saving interest is beneficial, users should consider inflation. If inflation is high, the future value of the money saved might be less than its current value. Additionally, individuals might consider the opportunity cost – could investing the extra payment yield higher returns than the interest saved on the loan? This involves risk assessment and personal financial goals. For instance, a mortgage with a 3% interest rate might be less urgent to pay off if you anticipate earning 7%+ in the stock market over the long term, though paying off debt offers a guaranteed return equal to the interest rate.
  7. Fees and Taxes: The calculator typically doesn't account for potential tax deductions (like mortgage interest) or other fees associated with loans. These can slightly alter the net financial benefit.
  8. Cash Flow and Financial Stability: The ability to make extra payments depends heavily on an individual's consistent cash flow and financial stability. Committing to extra payments should not jeopardize essential living expenses or emergency savings.

Understanding these factors helps users interpret the calculator's output realistically and integrate extra payments into a broader financial strategy.

Frequently Asked Questions (FAQ)

Q1: How do I ensure my extra payments are applied to the principal?

A: The best way is to explicitly state this when making the payment or contact your lender directly. Many lenders allow you to specify this in your online payment portal or via written instruction. If you simply send a larger check, it might be applied to your next scheduled payment instead of reducing the principal. Always confirm with your lender.

Q2: Is it always a good idea to make extra payments?

A: Generally, yes, especially for high-interest debt. Paying down debt offers a guaranteed return equal to the interest rate. However, consider prioritizing emergency savings and investing in opportunities that may offer higher potential returns than your loan's interest rate (while acknowledging the risk involved). It depends on your overall financial situation and risk tolerance.

Q3: Can I use this calculator for student loans or personal loans?

A: Absolutely! This extra payments calculator is designed for any standard installment loan where you make regular payments over a set period, including mortgages, auto loans, student loans, and personal loans. As long as the loan has a fixed interest rate and amortizes, the principles apply.

Q4: What if my loan has a variable interest rate?

A: This calculator is most accurate for fixed-rate loans. If you have a variable-rate loan, your interest rate can change, affecting your payment schedule and the total interest paid. While making extra payments is still beneficial, the exact savings and payoff time will fluctuate. You might need to adjust your extra payment amount periodically.

Q5: Does the calculator account for bi-weekly payments?

A: This specific calculator focuses on a single, fixed "Extra Monthly Payment." However, a common strategy is to pay half of your monthly payment every two weeks. This results in 26 half-payments per year, equivalent to 13 full monthly payments annually (one extra full payment). You can simulate this by setting your "Extra Monthly Payment" to roughly 1/12th of your regular monthly payment.

Q6: What is the difference between paying extra towards principal vs. making a larger total payment?

A: When you make an "extra payment" specifically designated for principal, it directly reduces the outstanding loan balance. This means less interest accrues in the future. If you simply pay more than your scheduled amount without designating it for principal, your lender might apply it to future interest or payments, negating the benefit. The calculator assumes the extra amount reduces the principal.

Q7: How does paying off a loan faster affect my credit score?

A: Paying off loans faster generally has a positive impact on your credit score. It reduces your overall debt burden and demonstrates responsible credit management. However, drastically shortening the life of a loan might slightly reduce the average age of your credit accounts, which is a minor factor.

Q8: Can I use the results from the calculator for tax purposes?

A: The calculator provides estimates of interest paid. For tax purposes, you should always rely on official statements provided by your lender (e.g., Form 1098 for mortgage interest). This calculator is for planning and estimation, not official reporting.

Related Tools and Internal Resources

function formatCurrency(amount) { return "$" + amount.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,'); } function formatNumber(num, decimals = 2) { return num.toFixed(decimals).replace(/\d(?=(\d{3})+\.)/g, '$&,'); } function calculateLoanPayment(P, r, n) { var monthlyRate = r / 1200; if (monthlyRate === 0) return P / n; var payment = P * monthlyRate / (1 – Math.pow(1 + monthlyRate, -n)); return isNaN(payment) ? 0 : payment; } function isValidNumber(value) { return !isNaN(parseFloat(value)) && isFinite(value); } function validateInput(id, errorId, minValue = null, maxValue = null) { var input = document.getElementById(id); var errorSpan = document.getElementById(errorId); var value = parseFloat(input.value); var isValid = true; errorSpan.textContent = "; if (input.value === "") { errorSpan.textContent = "This field is required."; isValid = false; } else if (!isValidNumber(value)) { errorSpan.textContent = "Please enter a valid number."; isValid = false; } else if (minValue !== null && value maxValue) { errorSpan.textContent = "Value cannot exceed " + formatCurrency(maxValue) + "."; isValid = false; } if (isValid) { input.style.borderColor = '#ccc'; } else { input.style.borderColor = 'red'; } return isValid; } function calculateExtraPayments() { var loanAmount = parseFloat(document.getElementById("loanAmount").value); var interestRate = parseFloat(document.getElementById("interestRate").value); var remainingTermMonths = parseInt(document.getElementById("remainingTermMonths").value); var extraPayment = parseFloat(document.getElementById("extraPayment").value); var validationPassed = true; validationPassed &= validateInput("loanAmount", "loanAmountError", 0); validationPassed &= validateInput("interestRate", "interestRateError", 0); validationPassed &= validateInput("remainingTermMonths", "remainingTermMonthsError", 1); validationPassed &= validateInput("extraPayment", "extraPaymentError", 0); if (!validationPassed) { return; } var monthlyRate = interestRate / 1200; var scheduledPayment = calculateLoanPayment(loanAmount, interestRate, remainingTermMonths); // Calculate Original Totals var originalTotalInterest = 0; var currentBalance = loanAmount; var tempMonths = remainingTermMonths; var tempMonthlyRate = monthlyRate; var tempP = loanAmount; var tempN = remainingTermMonths; if (tempMonthlyRate > 0) { var calculatedScheduledPayment = tempP * tempMonthlyRate / (1 – Math.pow(1 + tempMonthlyRate, -tempN)); } else { var calculatedScheduledPayment = tempP / tempN; } for (var i = 0; i < remainingTermMonths; i++) { var interestThisMonth = currentBalance * monthlyRate; var principalThisMonth = calculatedScheduledPayment – interestThisMonth; originalTotalInterest += interestThisMonth; currentBalance -= principalThisMonth; if (currentBalance < 0) currentBalance = 0; } var originalTotalCost = loanAmount + originalTotalInterest; // Calculate New Totals with Extra Payment var newTotalInterest = 0; var newMonths = 0; currentBalance = loanAmount; var totalPayment = scheduledPayment + extraPayment; if (monthlyRate === 0) { newMonths = loanAmount / totalPayment; newTotalInterest = 0; } else { var tempTotalPayment = scheduledPayment + extraPayment; if (tempTotalPayment remainingTermMonths * 5) { // Prevent infinite loop for edge cases, cap at generous estimate newMonths = remainingTermMonths; newTotalInterest = originalTotalInterest; } else { // Simulate amortization for new total interest calculation for (var i = 0; i currentBalance) { principalPaidThisMonth = currentBalance; } if (totalPayment > currentBalance + interestThisMonth) { // Adjust if total payment is more than needed for final payment totalPayment = currentBalance + interestThisMonth; } newTotalInterest += interestThisMonth; currentBalance -= principalPaidThisMonth; if (currentBalance 0 ? timeSaved + " months" : "0 months"; document.getElementById("primaryResult").textContent = formatCurrency(interestSaved); generateAmortizationTable(loanAmount, interestRate, remainingTermMonths, extraPayment, totalPayment, newMonths); updateChart(loanAmount, interestRate, remainingTermMonths, extraPayment, totalPayment, newMonths); } function generateAmortizationTable(loanAmount, interestRate, originalTerm, extraPayment, totalPayment, newTerm) { var tableBody = document.getElementById("amortizationTableBody"); tableBody.innerHTML = ""; // Clear previous table data var monthlyRate = interestRate / 1200; var currentBalance = loanAmount; var originalTotalInterestPaid = 0; var newTotalInterestPaid = 0; var monthsCount = 0; var scheduledPayment = calculateLoanPayment(loanAmount, interestRate, originalTerm); if (monthlyRate === 0) { scheduledPayment = loanAmount / originalTerm; } var paymentToApply = scheduledPayment + extraPayment; // If extra payment results in zero savings or is not beneficial, revert to scheduled if (interestRate > 0 && paymentToApply 0) { paymentToApply = scheduledPayment; // Ensure payment covers interest } if (paymentToApply <= 0) paymentToApply = scheduledPayment; // Ensure positive payment for (var i = 0; i 0.01; i++) { monthsCount = i + 1; var interestThisMonth = currentBalance * monthlyRate; var principalPaidThisMonth = paymentToApply – interestThisMonth; // Adjust for the final payment if (principalPaidThisMonth > currentBalance) { principalPaidThisMonth = currentBalance; paymentToApply = interestThisMonth + principalPaidThisMonth; } if (paymentToApply > currentBalance + interestThisMonth) { // Ensure final payment doesn't exceed needed amount paymentToApply = currentBalance + interestThisMonth; } if (principalPaidThisMonth < 0) principalPaidThisMonth = 0; // Should not happen with valid inputs if (paymentToApply < 0) paymentToApply = 0; currentBalance -= principalPaidThisMonth; if (currentBalance < 0) currentBalance = 0; originalTotalInterestPaid += (scheduledPayment – (loanAmount – (i 0 ? (currentBalance + principalPaidThisMonth) : 0)); // Calculate starting balance for this row cellPayment.textContent = formatCurrency(paymentToApply); cellPrincipal.textContent = formatCurrency(principalPaidThisMonth); cellInterest.textContent = formatCurrency(interestThisMonth); cellEndBalance.textContent = formatCurrency(currentBalance); } if (monthsCount === 0) { // Handle case where loan is already paid off or inputs are zero var row = tableBody.insertRow(); row.insertCell(0).textContent = "N/A"; row.insertCell(1).textContent = "$0.00"; row.insertCell(2).textContent = "$0.00"; row.insertCell(3).textContent = "$0.00"; row.insertCell(4).textContent = "$0.00"; row.insertCell(5).textContent = "$0.00"; } } function updateChart(loanAmount, interestRate, originalTerm, extraPayment, totalPayment, newTerm) { var canvas = document.getElementById('amortizationChart'); if (!canvas) return; // Canvas element might not exist if rendering server-side or error var ctx = canvas.getContext('2d'); if (!ctx) return; // Context not available // Clear previous chart if it exists ctx.clearRect(0, 0, canvas.width, canvas.height); var chartWidth = canvas.width; var chartHeight = canvas.height; // Data preparation var labels = []; var principalPaidOriginal = []; var principalPaidNew = []; var monthlyRate = interestRate / 1200; var scheduledPayment = calculateLoanPayment(loanAmount, interestRate, originalTerm); if (monthlyRate === 0) { scheduledPayment = loanAmount / originalTerm; } var currentBalanceOriginal = loanAmount; var currentBalanceNew = loanAmount; var originalTotalInterest = 0; var newTotalInterest = 0; // Simulate original loan for (var i = 0; i 0.01; i++) { labels.push(i + 1); principalPaidOriginal.push(loanAmount – currentBalanceOriginal); // Track cumulative principal paid var interestThisMonth = currentBalanceOriginal * monthlyRate; var principalThisMonth = scheduledPayment – interestThisMonth; originalTotalInterest += interestThisMonth; currentBalanceOriginal -= principalThisMonth; if (currentBalanceOriginal < 0) currentBalanceOriginal = 0; } // Simulate new loan for (var i = 0; i 0.01; i++) { var interestThisMonth = currentBalanceNew * monthlyRate; var principalPaidThisMonth = totalPayment – interestThisMonth; if (principalPaidThisMonth > currentBalanceNew) { principalPaidThisMonth = currentBalanceNew; } if (totalPayment > currentBalanceNew + interestThisMonth) { totalPayment = currentBalanceNew + interestThisMonth; } newTotalInterest += interestThisMonth; currentBalanceNew -= principalPaidThisMonth; if (currentBalanceNew < 0) currentBalanceNew = 0; principalPaidNew.push(loanAmount – currentBalanceNew); // Track cumulative principal paid } // Ensure arrays have the same length for plotting, fill with last known value if needed var maxLen = Math.max(labels.length, principalPaidOriginal.length, principalPaidNew.length); while (labels.length < maxLen) labels.push(labels.length + 1); while (principalPaidOriginal.length < maxLen) principalPaidOriginal.push(principalPaidOriginal[principalPaidOriginal.length – 1] || 0); while (principalPaidNew.length < maxLen) principalPaidNew.push(principalPaidNew[principalPaidNew.length – 1] || 0); // Drawing the chart (simple bar chart using canvas API) var barWidth = (chartWidth * 0.8) / maxLen; var chartAreaHeight = chartHeight * 0.7; var yAxisMax = loanAmount * 1.1; // Slightly more than the loan amount for scaling ctx.font = '12px Arial'; ctx.fillStyle = '#333'; // Draw X Axis ctx.beginPath(); ctx.moveTo(chartWidth * 0.1, chartHeight * 0.9); ctx.lineTo(chartWidth * 0.9, chartHeight * 0.9); ctx.strokeStyle = '#333'; ctx.stroke(); ctx.fillText('Month', chartWidth * 0.5, chartHeight * 0.95); // Draw Y Axis ctx.beginPath(); ctx.moveTo(chartWidth * 0.1, chartHeight * 0.9); ctx.lineTo(chartWidth * 0.1, chartHeight * 0.1); ctx.strokeStyle = '#333'; ctx.stroke(); ctx.fillText('Cumulative Principal Paid ($)', chartWidth * 0.05, chartHeight * 0.1); // Draw bars for Original Loan ctx.fillStyle = 'rgba(0, 74, 153, 0.6)'; // Primary blue for (var i = 0; i 0) { ctx.fillRect(x, y, barWidth * 0.45, barHeight); } // Draw Month Labels if (i % Math.ceil(maxLen / 10) === 0 || i === principalPaidOriginal.length – 1) { // Label roughly 10 times ctx.fillStyle = '#333'; ctx.fillText(labels[i], x + (barWidth * 0.45) / 2, chartHeight * 0.9 + 15); ctx.fillStyle = 'rgba(0, 74, 153, 0.6)'; // Reset color } } // Draw bars for New Loan (shifted slightly) ctx.fillStyle = 'rgba(40, 167, 69, 0.6)'; // Success green for (var i = 0; i 0) { ctx.fillRect(x, chartHeight * 0.9 – barHeight, barWidth * 0.45, barHeight); } } // Legend ctx.fillStyle = '#333'; ctx.fillText('Original Loan', chartWidth * 0.1, chartHeight * 0.05); ctx.fillStyle = 'rgba(0, 74, 153, 0.6)'; ctx.fillRect(chartWidth * 0.1, chartHeight * 0.06, 15, 8); ctx.fillStyle = '#333'; ctx.fillText('With Extra Payments', chartWidth * 0.3, chartHeight * 0.05); ctx.fillStyle = 'rgba(40, 167, 69, 0.6)'; ctx.fillRect(chartWidth * 0.3, chartHeight * 0.06, 15, 8); } function resetCalculator() { document.getElementById("loanAmount").value = "200000"; document.getElementById("interestRate").value = "4.5"; document.getElementById("remainingTermMonths").value = "360"; document.getElementById("extraPayment").value = "100"; // Clear errors document.getElementById("loanAmountError").textContent = ""; document.getElementById("interestRateError").textContent = ""; document.getElementById("remainingTermMonthsError").textContent = ""; document.getElementById("extraPaymentError").textContent = ""; // Reset input borders document.getElementById("loanAmount").style.borderColor = '#ccc'; document.getElementById("interestRate").style.borderColor = '#ccc'; document.getElementById("remainingTermMonths").style.borderColor = '#ccc'; document.getElementById("extraPayment").style.borderColor = '#ccc'; calculateExtraPayments(); // Recalculate with defaults } function copyResults() { var loanAmount = document.getElementById("loanAmount").value; var interestRate = document.getElementById("interestRate").value; var remainingTermMonths = document.getElementById("remainingTermMonths").value; var extraPayment = document.getElementById("extraPayment").value; var originalTotalInterest = document.getElementById("originalTotalInterest").textContent; var originalTotalCost = document.getElementById("originalTotalCost").textContent; var newTotalInterest = document.getElementById("newTotalInterest").textContent; var interestSaved = document.getElementById("interestSaved").textContent; var timeSaved = document.getElementById("timeSaved").textContent; var primaryResult = document.getElementById("primaryResult").textContent; var assumptions = "Assumptions:\n"; assumptions += "- Current Loan Balance: $" + loanAmount + "\n"; assumptions += "- Annual Interest Rate: " + interestRate + "%\n"; assumptions += "- Remaining Term: " + remainingTermMonths + " months\n"; assumptions += "- Extra Monthly Payment: $" + extraPayment + "\n"; var resultsText = "Extra Payments Calculator Results:\n"; resultsText += "Estimated Interest Saved: " + primaryResult + "\n"; resultsText += "————————————\n"; resultsText += originalTotalInterest + "\n"; resultsText += originalTotalCost + "\n"; resultsText += newTotalInterest + "\n"; resultsText += interestSaved + "\n"; resultsText += timeSaved + "\n"; resultsText += "————————————\n"; resultsText += assumptions; navigator.clipboard.writeText(resultsText).then(function() { alert('Results copied to clipboard!'); }).catch(function(err) { console.error('Failed to copy: ', err); alert('Failed to copy results. Please copy manually.'); }); } // Initialize calculator on page load window.onload = function() { resetCalculator(); // Set sensible defaults and calculate initial results // Ensure canvas has a default size if not set in CSS var canvas = document.getElementById('amortizationChart'); if (canvas) { canvas.width = 700; canvas.height = 300; } };

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