This calculator helps you estimate how long it will take to pay off your credit card debt and the total interest you'll pay, considering your current balance, interest rate, minimum monthly payment, and any additional payments you can make.
How it Works: The Math Behind the Calculator
The calculator uses an iterative process to simulate month-by-month payments. Each month, the following calculations occur:
Calculate Monthly Interest: The annual interest rate is converted to a monthly rate by dividing by 12. This monthly rate is then applied to the current balance to determine the interest accrued for that month.
Monthly Interest = Current Balance * (Annual Interest Rate / 100 / 12)
Calculate Total Payment: The total payment for the month is the sum of the minimum monthly payment and any additional payment you've decided to make.
Total Payment = Minimum Monthly Payment + Additional Monthly Payment
Apply Payment: The total payment is applied first to the accrued interest, and then the remainder is applied to reduce the principal balance.
Principal Paid = Total Payment - Monthly Interest
Update Balance: The new balance is the previous balance minus the principal paid.
New Balance = Current Balance - Principal Paid
Check for Completion: If the new balance is zero or less, the debt is paid off. Otherwise, the process repeats for the next month.
The calculator tracks the number of months and sums up all the interest paid to provide you with an estimated payoff timeline and total interest cost.
Why Use This Calculator?
Visualize Progress: See how long it might take to become debt-free.
Impact of Extra Payments: Understand the significant difference even small additional payments can make over time.
Total Interest Costs: Estimate the true cost of your debt, highlighting the importance of paying it down quickly.
Budgeting: Help plan your finances by knowing your debt repayment schedule and total interest burden.
By entering your specific credit card details, you can gain valuable insights into managing and eliminating your credit card debt more effectively.
function calculateRepayment() {
var currentBalance = parseFloat(document.getElementById("currentBalance").value);
var annualInterestRate = parseFloat(document.getElementById("annualInterestRate").value);
var minimumMonthlyPayment = parseFloat(document.getElementById("minimumMonthlyPayment").value);
var additionalMonthlyPayment = parseFloat(document.getElementById("additionalMonthlyPayment").value) || 0; // Default to 0 if empty or invalid
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = "; // Clear previous results
// Input validation
if (isNaN(currentBalance) || currentBalance <= 0) {
resultDiv.innerHTML = 'Please enter a valid current balance greater than zero.';
return;
}
if (isNaN(annualInterestRate) || annualInterestRate < 0) {
resultDiv.innerHTML = 'Please enter a valid annual interest rate (0% or higher).';
return;
}
if (isNaN(minimumMonthlyPayment) || minimumMonthlyPayment <= 0) {
resultDiv.innerHTML = 'Please enter a valid minimum monthly payment greater than zero.';
return;
}
if (isNaN(additionalMonthlyPayment) || additionalMonthlyPayment < 0) {
resultDiv.innerHTML = 'Please enter a valid additional monthly payment (0 or higher).';
return;
}
var monthlyInterestRate = annualInterestRate / 100 / 12;
var totalMonthlyPayment = minimumMonthlyPayment + additionalMonthlyPayment;
var months = 0;
var totalInterestPaid = 0;
var balance = currentBalance;
// Check if total payment is less than minimum interest on the first month, which can lead to infinite loop
var firstMonthInterest = balance * monthlyInterestRate;
if (totalMonthlyPayment 0) {
var interestThisMonth = balance * monthlyInterestRate;
totalInterestPaid += interestThisMonth;
var principalPaid = totalMonthlyPayment – interestThisMonth;
// Ensure principal paid doesn't exceed the balance
if (principalPaid > balance) {
principalPaid = balance;
}
balance -= principalPaid;
months++;
// Safety break for extremely large calculations or edge cases
if (months > 10000) {
resultDiv.innerHTML = 'Calculation exceeded maximum iterations. Please check your inputs.';
return;
}
}
var years = Math.floor(months / 12);
var remainingMonths = months % 12;
var payoffTime = "";
if (years > 0) {
payoffTime += years + " year" + (years > 1 ? "s" : "");
if (remainingMonths > 0) {
payoffTime += ", ";
}
}
if (remainingMonths > 0) {
payoffTime += remainingMonths + " month" + (remainingMonths > 1 ? "s" : "");
}
if (payoffTime === "") {
payoffTime = "less than a month"; // Should only happen if balance was 0 initially
}
resultDiv.innerHTML = 'Estimated Payoff Time: ' + payoffTime + '' +
'Total Interest Paid: $' + totalInterestPaid.toFixed(2) + '';
}