How this calculator works
Each month the card charges interest on the opening balance, then your payment reduces what is left. With a fixed payment the amount stays the same and the share going to principal grows. With a minimum payment the amount is usually a percentage of the statement balance with a dollar floor, so it shrinks as the balance shrinks and payoff can take decades. The model assumes no new purchases, no fees and a constant APR. Real statements calculate interest on a daily balance and apply a grace period to new purchases, so a lender quote will differ.
Formula
Monthly rate i = APR / 12. Each month: interest = opening balance × i; minimum payment = max(floor, opening balance × percentage); payment = min(scheduled payment, balance + interest); new balance = balance + interest - payment. Repeat until the balance reaches zero. Total interest is the sum of monthly interest charges.
Worked example
Paying a fixed $250 a month on $5,000 at 19.99% clears the balance in 25 months, with $1,132.29 of interest and $6,132.29 paid in total. The final payment is $132.29 instead of $250. Choosing the minimum instead, at 2% of the balance with a $25 floor, starts at $100 a month and takes 523 months, costing $20,151.45 in interest. The gap between the two outcomes is the reason the method is a separate choice.
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Frequently asked questions
Why does the minimum payment keep falling?
It is a percentage of the outstanding balance, so as the balance drops the minimum drops too. That extends repayment and increases total interest compared with a fixed payment.
Does the calculator handle new spending?
No. It assumes the card is not used again and no annual fees, late fees or penalty rates apply. Adding purchases can keep the balance flat indefinitely.
Why is the first payment shown separately?
The final payment is usually smaller than the scheduled one because it only clears what is left. Showing the first payment lets you confirm the schedule starts where you expect.
Is interest charged before the payment?
Yes. Posting interest on the opening balance and then applying the payment is the conservative monthly model used by most payoff estimates.