In the United States, a credit score is a number that summarizes information found on a person's credit report. The higher the number, the lower the risk of lending money to that person.

The most widely used credit score appears to be the Classic FICO score, a formula whose rights are owned by its creator, the Fair Isaac Corporation. The broad-based credit bureau risk score was first deployed in 1989 by Equifax under the name BEACON. Today, it is the lingua FICO in casual conversation, for mortgage loan evaluation by Fannie Mae and Freddie Mac, and it is even mentioned by name by the U.S. Department of Housing and Urban Development. Not only is the algorithm used in the primary, consumer market, it is a standard of quality of investment market instruments.

Scale and Range

As stated by Fair Isaac, the FICO score scale is 300 to 850, and thus, the range is 550 (technically, 551, if the two extremes are included). The reason for the peculiarly odd scale is, perhaps, to differentiate it from other credit scores—although the FICO's extreme success and ubiquity make that irrelevant. FICO sued a competitor over the idea of the 300-850 scale.

While the general FICO is a general purpose score, Fair Isaac sells other algorithms (formulas) for specific markets. Auto and credit card ("bankcard") score models by the company have their own, equally esoteric mumbers: 250 to 900. Closer still to a logical 0-1000 scale, the FICO NextGen is 150-950.

Within the basic FICO score realm, there are new and old versions ("models"), including FICO 8.

Consumer access

Before 2001, citizens had no access to their FICO score. The theory is an old one: A person who knows he is watched acts differently than he would otherwise. Merely asking for one's score was met with flat-out refusal. A victim of its own success, Fair Isaac relented, and, again with Equifax, provided the BEACON FICO to citizens. Access to the TransUnion (then Trans Union) version of the FICO followed the following year, 2002. And, completing the troika, Experian provided it in 2003, although that access ended in 2009.

Other credit score brands

With the national obsession in credit scores, Fair Isaac's competitors see a huge market for selling credit scores to consumers. Unfortunately, the players don't all have a contract. So, picking up the crumbs are FICO-exile Experian, selling its PLUS "educational" score from its home page, TransUnion providing VantageScore, and others. But, for consumers, since there is access to the favored credit score, there is not much of a point.

Improving one's credit score

Today, a decade after the release of the FICO to consumers, there are any number of resources to improve your credit score. Disclosures recently required by federal law provide insights to financial service applicants. Fair Isaac even maintains a forum for citizens to discuss credit scores and their many facets.

But perhaps the best–and certainly the most expedient–way to attempt to solve the mystery of your credit score is to use the FICO score simulators. While a small fee is required, they are the only known tool providing direct access to your credit report, credit score, reasons that it is not higher and suggestions to improve it. The simulators give a general suggestion for improvement, and allow you to submit what-if scenarios to determine the likely outcome of particular actions (i.e., what if I get another credit card, pay down a balance, pay off an account, miss payments, etc.).

The information available will only get a person so far, though. In this bleak landscape, even the average score is unknown to the public.

What is a good credit score?

What score it takes to get the best interest rate is the essential question, although some strive and stumble for the heights for vanity or sport. But a score is just a score—there is no good or bad unless you consider the extremes: 300 is definitely bad, and 850 is, to be sure, good. It is possible to have no score, too (if you have no credit history or one insufficient enough to score it).

So, good in this ranking system is in the eye of the one who holds the gold. Fortunately, to find out what that means, recent legislation created a fairer playing field between banks and consumers: Mandatory disclosures that provide information about a person's credit score used in the actual lending process include where the person stands in relation to the population, who provided the score and, of course, the score itself. It's not perfect and took too long to happen, but it's a start.