Why the minimum is designed to shrink
Most card minimums are a percentage of the balance, or 1% of the balance plus that month's interest. As the balance falls, the minimum falls with it. So the payment is always just big enough to keep things moving and never big enough to finish quickly. Paying the minimum isn't a mistake. It's the slowest way out that the card company allows.
The box on your statement
Federal rules under the Credit CARD Act make card issuers print a Minimum Payment Warning on every statement. It shows how long the minimum would take, and the monthly payment that would clear the balance in 36 months. The third column in the table does the same job, so you can check it against your statement.
The one habit that fixes most of it
Pick a dollar amount and pay that every month, whatever the minimum says. When the minimum falls, your payment doesn't. That single change is where most of the saving in the table comes from.
After a rate rise
Most card rates follow the prime rate, so a Fed rise makes this trap slightly worse overnight. Change the rate box by 0.25% and watch the interest line move.
