How to use it
Even a small extra payment can move your debt-free date months earlier, because it cuts the balance the interest is charged on. Use the extra payment box to compare. The estimate assumes the rate stays the same, interest compounds monthly (APR / 12) and you add no new charges.
Questions
How is the debt-free date calculated?
Each month interest (APR / 12) is added and your payment is subtracted, until the balance reaches zero. The number of months is added to the current date.
Why does it say never?
Your payment is smaller than the interest charged each month, so the balance would keep growing.
Is this exact?
It is an estimate. Real statements depend on billing dates, daily interest and fees.