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Credit scores: How three numbers rule your life
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If you thought grades only mattered in school, think again. A credit score — essentially a grade on your creditworthiness — is a deciding factor in many financial transactions throughout your life.

FICO scores, the most widely used scores, start at 300 and go to 850. Of course, the higher the number, the better. A score of 760 or more is considered the top range, and those borrowers get the best interest rates and terms.

For a $300,000 mortgage, a person with a top score would pay $100 less a month for 30 years than someone with a score of 660, according to myFICO, the consumer division of FICO.

But credit scores determine more than just loans.

"Look around at your telephone, your car, the house you live in — your credit score played a role in you being able to obtain those things," noted Rod Griffin, director of public education for Experian, one of the three credit-reporting agencies.

To get your score, you can buy one from myFICO for $19.95 or use a credit-tracking site like Credit Karma that approximates your score for free. Another option: Get a credit card, such as Discover or Chase Slate, which includes a credit score with each month's bill.

Here are all the ways that credit scores come into play beyond loans.

Renting an apartment. A landlord wants to know whether you'll pay your rent on time or if you're the type who throws all-nighters. A credit score is a good predictor of those behaviors.

"If your scores aren't good, you might have to pay an extra security deposit," Griffin said.

But don't wait for a landlord to suggest it.

"If you know that credit is an issue, you may be able to help yourself by offering an extra deposit," said Gerri Detweiler, head of market education at Nav, which helps small businesses access financing.

Young renters without much credit history might have a low score, noted certified financial planner Pamela Sandy, founder of Confiance. Parents might want to help out.

"You might need to guarantee the lease to get your kids off and running," she said. "But remember, it's an obligation and you have to be prepared that your kid turns out to be a deadbeat."

After a year of on-time payments, the landlord should agree to remove you from the lease.

Buying insurance. Insurers make money when they don't pay out claims, so their best customers are people who don't file claims. So how is a credit score relevant?

It turns out there's a correlation between low scores and the likelihood of filing a claim, so it's a factor in setting your premium rate for auto and homeowner's insurances (except in California, Hawaii and Massachusetts, where state law prohibits the practice).