It's not always best to pay off the debt with the biggest interest. The amount of debt also plays a factor since $20,000 at 10% will be bigger monthly payments and more interest than 5,000 at 20%. So you need to know the interest of each credit card and the balance and then calculate the interest on each amount of debt. Then calculate how much interest you will have to pay after you make a payment. See which option has you paying the least amount of interest. In the end interest is like throwing your money out the window of a moving car. So if you're paying $166 a month that is like handing people walking by on the street your hard earned money.