Credit Card Interest Calculator: What If I Pay Only the Minimum Due?

Each month, interest is charged on the balance you carry at the card's monthly rate, and GST is charged on that interest. The minimum due covers at least that month's interest and GST, so paying it never makes the balance grow, but very little goes towards the balance itself.

While a balance is carried, the interest-free period is lost: The interest-free credit period is suspended if any balance of the previous month's bill is outstanding. New purchases are therefore charged interest from the day you make them; the calculator counts half a month on average.

If your payment does not cover the interest, GST and new spends, the balance never clears, and the calculator says so instead of running for ever.