Most credit cards offer a fixed interest rate, meaning that there is a single, unchanging percentage charged on your purchases. With a variable rate create card, on the other hand, the rate you are charged on unpaid balances can change based on a few factors. Typically, the rate is tied to the prime rate, which fluctuates, with an additional fixed percentage on top. For example, a card might charge the bank’s prime rate plus 5%. Also, your credit score plays a role in determining how low of a rate you can get. There’s a simple reason to consider a variable rate card: If you have an excellent credit score, you could land some of the lowest rates available in the credit card market. However, if you don’t have a great credit score, you want to keep things simple or need a card that also comes with a great balance transfer promotion, you may want to consider one with a fixed rate.