Many credit cards come with special introductory rates. These often include low or 0% interest rates for the first months or year. But what happens after the introductory period? This is when most credit cards switch to a variable or fixed interest rate. Read on to learn the difference between variable and fixed rate credit cards.

Variable Rate Credit Cards

Variable interest rates are usually tied to another rate. Many credit card companies use the Prime lending rate as an index. This is the rate at which top banks in the United States can borrow money from the Federal Reserve. Creditors also may calculate variable interest rates based on the Treasury bill.

The credit card lender adds a number of percentage points, known as the margin, to the index rate. This new rate is then passed on to your credit card. In certain cases, the credit card company may first multiply the index rate by another number, called the multiple. The new figure is added to the margin to determine the credit card interest rate.

As the index rate fluctuates, it affects the rate on your credit card. The APR (annual percentage rate) on variable rate credit cards may change at any time. These cards often include a "floor rate." This is the lowest interest rate that can be offered.

Fixed Rate Credit Cards

Unlike the variable rate, which is subject to change at any time, the fixed rate credit card offers one set rate. The initial rate is sometimes a couple of percentage points higher than a variable rate. However, the advantage is that a fixed rate may not change as quickly as the variable rate credit card.

That said, fixed rates do sometimes change. The credit card company may include the right to change the rate in the card plan. According to the Truth in Lending Act, the lender must provide at least 15 days notice before raising the rate. So make sure to look through the apparent "junk mail" you receive. It could include an announcement that your rate is about to change.

Decide which Rate is Best for You

To decide which rate will fit you best, consider the market fluctuations. The current average rate for variable rate credit cards is 14.72%. The average rate on fixed rate credit cards is 13.33%. Some experts advise getting a fixed rate credit card for its stability. Others suggest opting for a variable rate credit card when interest rates are dropping.

If you are considering a variable rate credit card, first check to see if there are caps on how high or low the interest can go. If the lowest possible rate on the card is 16%, and rates are dropping, you may want to look into other options.

Whether you decide on a variable or fixed rate credit card, be sure to read through the fine print. This will help you find rate fluctuation policies. Some card plans will change the rate after late or missed payments.

If you pay off your balances each month, the interest rate on your credit card will affect you less. However, if you regularly carry a balance (and most Americans do), it is important to understand the difference between variable and fixed rates. Doing so will ensure you are getting the best deal on interest charges.