Credit Card Payoff

This tool helps plan paying off a credit card balance. In Time mode it takes the current balance, APR, and a monthly payment, then tells you how many months it will take to clear the balance, the total interest paid, and the total amount paid. In Payment mode it takes the balance, APR, and a target number of months, then tells you the fixed monthly payment needed to clear the balance in that time.

1. Enter Balance (current card balance, e.g. 5000). 2. Enter APR as a percentage (e.g. 18.9). 3. Pick a mode button: Time to Payoff or Monthly Payment. 4. In Time mode enter Monthly Payment; in Payment mode enter Desired Months. 5. Press Calculate. The result shows time to payoff (months, or years and months), total interest, and total paid. If the payment does not cover the monthly interest, the tool flags it and shows the minimum payment required.

Time mode uses months = ceil( -ln(1 - (r * B) / P) / ln(1 + r) ), where r = APR / 100 / 12, B is the balance and P is the monthly payment; total paid = P * months and total interest = total paid - B. Payment mode uses P = B * (r * (1 + r)^n) / ((1 + r)^n - 1), where n is the desired months. The tool refuses to compute Time mode if the monthly payment is at or below the monthly interest (B * r), because the balance would never decrease.