Under mounting pressure from credit bureaus, lending agencies, and legislators, Fair, Isaac & Co., the granddaddy of credit scoring, revealed to the public on Thursday its mysterious method of rating loan candidates.

And starting next month consumers will be able to log on to its Web site to learn their own Fico scores and why they got them.

Most lenders use the scores to approve or reject loans.

On Thursday the San Raphael, Calif., company posted a list of everything it evaluates when assigning a credit score and the relative weight it assigns to each aspect of a consumer's borrowing history. It said that "demystifying" the process will help consumers understand how their own scores were derived and how to raise them over time.

"Consumers have a right to understand their credit rating," said Tom Grudnowski, president and chief executive officer. "By expanding the consumer information on our Web site, we're giving consumers what they have asked for: a look at what goes into their credit scores."

Fair, Isaac has already listed the basic makeup of its scores on its Web site. The most important factor is the customer's payment "track record," which makes up 35% of the score. A couple of reasonably late payments however, will not damage the track record.

Next, Fair, Isaac looks at the amount owed on other accounts, which makes up 30% of the score. If a customer owes money to a variety of lenders, the score will not necessarily be lowered, but owing a great deal of many on many accounts can indicate that a person is overextended, Fair, Isaac said.

About 15% of the score is based on the length of the loan candidate's credit history. The remaining 20% is based on a few factors, including how recently a person has opened a credit line, and whether the person has a "healthy mix" of different types of loans.

The disclosure comes after a flurry of announcements by Trans Union Corp., Experian Inc., Fannie Mae, and Freddie Mac, all aimed at sharing more information with their customers about their credit scores, and challenging Fair, Isaac to do the same. In one particularly contentious statement made this year, Franklin D. Raines, the chairman and chief executive of Fannie Mae, called Fair, Isaac's scoring system "opaque," and said his agency would replace the Fico score with its own.

Last month the California Senate voted 31-1 in favor of legislation that would require disclosure of credit scores when consumers shop for mortgages. The legislation is now in the state Assembly, according to Fair, Isaac.

Fair, Isaac said it is not convinced that giving consumers their credit scores will clarify why they were denied a loan, but it has acquiesced under industry pressure.

"We still don't think the scores themselves do very much to help consumers, because they change all the time, and mean different things to different lenders," said Peter McCorkell, a senior counsel for Fair, Isaac. "We still have reservations about what is irreverently described as 'free range score disposal,' but we think it's inevitable that it's going to occur, so let's do it in the best possible way."

In answer to Mr. Raines' complaint about the scores being "opaque," Mr. McCorkell said: "We're challenging them to see just how transparent they're going to be, because we're making our scores really transparent."

Starting next month, customers will be able to receive their own score online, by submitting a copy of their credit report to Fair, Isaac. The company is discussing ways to directly access credit bureau reports with Trans Union, Equifax, and Experian, in order to make the process cheaper and easier for consumers, Mr. McCorkell said. The credit bureaus typically charge $8 to consumers who ask for their credit report. The reports are free to people who were recently denied credit.

Last month Chicago-based Trans Union said it would create its own credit score, along with an explanation of how the score was derived, in order to show consumers how they are viewed by lenders. Mr. McCorkell said this move was a bad idea, arguing that the system would only get more bewildering if individual credit bureaus devised their own scoring systems. Trans Union did not return phone calls requesting comment.

"We think there's lots of room for confusion here," Mr. McCorkell said. "Trans Union disclosing a set of scores to consumers that no other lender uses compounds the confusion and doesn't make it any better."

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