How long will it take to pay off my credit card?

Slide the payment down toward the monthly interest. Watch the payoff time shoot up.

Challenge: Pay the card off in 24 months or less. The box under the picture turns green when you get it.

Stuck? Pick one of the examples from the “Try an example” menu, or press “New example.”

Each month the card multiplies your balance by $1 + i$ and then subtracts your payment. Written out, the balance after $n$ months has $(1 + i)^n$ in it. To find when it reaches zero, you have to solve for the exponent $n$, and that takes a logarithm:

$$n = -\frac{\ln\left(1 - \frac{iB}{P}\right)}{\ln(1 + i)}$$

The fraction $iB/P$ is the share of your first payment eaten by interest. As the payment falls toward the interest, that share approaches 1. The logarithm then heads toward $\ln 0$, which has no value, and the payoff time runs off toward forever.

The dashed curve shows the same card with $50 more a month.

Enter the balance, the APR from your statement, and what you plan to pay each month. The last readout is the payment that clears the balance in 3 years.

• This assumes no new purchases, a fixed APR, and interest charged monthly on the balance.
• Real cards compute interest on the average daily balance, so your statement can differ by a few dollars.
• Promotional 0% rates usually end. Check what the rate becomes afterward.