02/26/2014 05:56 pm ET Updated Apr 28, 2014

5 Surprising Facts About Credit Scores and Credit Cards

Credit cards can be a bit of a tease. The top cards offer significant rewards, from free airfare to bonus points to 0 percent introductory rates. What they often don't tell you, however, is just how hard it is to qualify for these offers.

The underwriting standards are a closely guarded secret. Much like the Coca-Cola formula, credit card companies closely guard the criteria they use to approve applicants. While the exact details remain a secret, however, we do have some idea of the standards used. This information includes details about the credit scores of approved applicants.

One site,, has recently published a list of the lowest and average credit scores of approved applicants for some of the most exclusive card offers. Taken from data provided by Credit Karma, this information gives us some real insight into what it takes to nab the best reward deals.

Here are five things the data tells us.

1. The 700 club is not required

The average credit scores for the top cards typically range in the low 700s. The lowest approved scores, however, dip well into the 600s. Certainly other factors come into play, such as income and past payment history. But the top credit cards, such as cards from Discover, Citi and Barclaycard approve applicants with scores in the 600s.

2. The bigger the rewards, the higher the score

Not all rewards cards are created equal. The top rewards cards typically offer 2 percent points, miles or cash on virtually all purchases. As one would expected, the average credit score for these offers is notably higher than even other "good" or "excellent" credit credit cards. As an example, one version of the Barclaycard Arrival World MasterCard offers 2x miles on all purchases plus significant bonus miles. The average score of approved applicants is nearly 740.

3. The top 0 percent offers require a top credit score

The best 0 percent APR introductory offer available today runs for 18 months. These offers apply to both purchases and balance transfers. While these offers can help people trying to get out of credit card debt, they require a top credit score. The longest 0 percent offers from the likes of Discover and Citi, for example, have average scores in the lower to mid-700s. For those with average credit in the mid-600s, expect to qualify for a 0 percent offer that lasts just six months.

4. Student cards require lower scores
As one would expect, student credit cards require much lower scores. In fact, the available credit score data show that average scores for approved applicants fall below 700. And the lowest approved scores range in the low 600s and in some cases even below 600.

5. It's Not Just about approval

Getting approved for a card is just the start. Credit scores and other underwriting criteria also affect an applicant's credit limit and interest rate. High scores result in higher limits and lower rates. One site that gives data on credit limits and rates for various credit scores is called Who Gave Me Credit.

It's important to keep in mind, as noted above, that credit score information is just one factor in the underwriting criteria. In addition, these criteria continually change as card issuers fine-tune their underwriting standards and the interest rate environment changes.

Video Powered by Bank of America: