Here's one explanation of how the Fair Isaacs Corporation (FICO) does their numbering thing to give you a credit score (n.b.: this is not from them, they scrupulously avoid speaking about their proprietary system to outsiders). It's one guess of many in the open market:
"When determining how high a score will be, five characteristics separate the cream of the crop from everyone else. In order of score significance:
What does this mean for a consumer in search of a loan?
"Mortgages: By Freddie Mac standards, borrowers with FICO scores above 660 are likely to have an "acceptable" credit reputation and their loan files need only a basic review. The credit risk is "uncertain" for those with scores between 620 and 660, with a thorough review of the borrower's entire credit history. A score below 620 indicates "high risk" with an unacceptable credit reputation that could make traditional financing difficult to obtain.
Credit cards: Credit card lenders place additional weight on credit card-related information, such as how many times a person missed revolving credit payments. And the systems evaluate a college student targeted for a starter card differently than a platinum-toting stockbroker with a summer home in the Hamptons.
Auto lenders: Auto scores, on the other hand, focus on "deal characteristics" in much the same way the mortgage scores do, David Shellenberger, product manager at Fair, Isaac and Co., says. They take into account things such as the amount a customer puts down, for example, as well as a borrower's debt-to-income ratio, length of time at one job and the like. As with credit card lending, information about past performance on similar types of loans is weighted, so a missed Nissan payment might be more important than an overdue Visa bill."