How credit card payoff is calculated
Each month interest is added to your balance, then your payment is subtracted. Because interest is charged on the remaining balance, paying more each month cuts the time and interest sharply.
Worked example. A $3,000 balance at 19.99% APR, paying $150/month, clears in about 25 months and costs roughly $660 in interest. Bump the payment to $250 and it clears in about 14 months for far less interest.
The minimum-payment trap
Card minimums are typically 1–3% of the balance, often only just above the interest. On a high-APR card that means most of your payment is interest and the balance barely moves. Paying a fixed amount above the minimum is what actually clears the debt.