The most widely accepted and used credit score -- often referred to as the FICO score -- was created from a secret formula owned by the Fair Isaac Corp.

Nearly 50 years ago, founders Bill Fair and Earl Isaac discovered they could predict how likely a consumer was to miss a payment or default on a loan if they could collect enough information about that person's credit history.

As a result, your FICO score is based on what banks, stores, utility companies and other creditors tell the three major credit-reporting agencies about how much you owe and how diligently you pay your bills.

Anyone who has ever had a credit card, auto loan, or even an electric bill in their name has a credit history with Experian, TransUnion and Equifax. And if you have a credit history, you have a FICO score attached to your file.

The higher the score, the better your credit.

While it's theoretically possible to earn a perfect 850, a score above 720 is usually good enough to qualify for the best rates on just about any loan.

But if your FICO score is below 620, you're in the dreaded subprime category where you'll be charged higher-than-average rates -- if you can get a loan at all.

Your score is calculated using 22 variables from your credit history.

The most important factors are:

Payment history (35%). You want a long record of paying your bills on time with no missed payments. If you don't pay on time, the length of time payments are past due, the amount that's delinquent and the number of past-due items all affect your score.

How much of your available credit you've used (30%). The closer you are to your credit limits, the lower your score. FICO begins to penalize you anytime you borrow more than 50% of your available credit.

Length of credit history (15%). Having accounts open for a long time increases your credit score, although inactive accounts don't help as much as active ones. The score looks at how long you've had your oldest account as well as the average age of all your accounts.

New credit (10%). Opening a bunch of new accounts in a short period decreases your credit score and makes lenders nervous. Even credit-report inquiries (when someone checks your credit history because you're trying to obtain credit) lower your score.

Thankfully, inquiries made by employers or lenders sending unsolicited offers don't affect your score. Neither do your requests for your own credit report. FICO also considers a flurry of inquiries from mortgage lenders as a single request, so you aren't penalized for seeking multiple bids on a home loan.

Types of credit used (10%). Your score will be a little higher if you have a record of repaying a range of debts, such as credit cards, auto loans and mortgages.

Take special notice of one thing that is not used to calculate your FICO score -- how much money you make. It doesn't matter whether you earn $10,000 or $10 million a year. Income is not a factor.