If you’re like most of us, you probably haven’t thought too much about your credit score. You’ve been more focused on getting your career started, enjoying your independence, and having fun.

But now, you’re a little older. The post-college fog has cleared, and you’re starting to think about major life decisions—decisions like buying a house or getting a new car.

Why your credit score is so important

Suddenly, your credit score seems a lot more important.  After all, the difference between an okay score and an excellent one could be the difference between a car or house payment you can afford, and one that puts unjustifiable strain on your budget.

It could even be the difference between getting approved for your dream home or renting for a few more years.

You don’t want any nasty surprises to derail an otherwise smooth transaction, so that’s why it’s important to know your credit score before you apply for a mortgage or a car loan. And you want to know the credit score that 90 percent of lenders see—your FICO® Score (See FICO Score with enrollment in Experian CreditWorksSM)!

Fortunately, it’s now easy—Experian offers a 7-day trial with enrollment in Experian CreditWorksSM, which gives users access to their FICO® Score and Experian Credit Report for $1, (with enrollment in Experian CreditWorksSM).

Now, you might be saying, why should I pay $1 when I can get my credit score for free from other competitors?

Let me tell you why:

Most competitors offer a VantageScore—it’s just another way of taking your annual credit report (which just reports your credit history, but doesn’t make any judgments or evaluations of that history) and turning it into a number. The Vantage Score was introduced in 2003 to compete against the long-dominant FICO score.

There’s nothing wrong with a VantageScore. It’s just another system for evaluating credit.  However, most lenders still use FICO.

Lisa Haydon, senior loan officer at Greenway Mortgage in Middletown, New Jersey., told CNBC, “Ninety percent of lenders use FICO. When my clients get their credit reports through a [free credit platform], they don’t use the same type of formula.”

The two scores are similar, but by no means the same. Both give you a number between 300 and 850, both base that number on your credit report, and both sell those numbers to credit card companies, mortgage lenders, and banks.

Haydon told CNBC that many of her clientele had been burned by using free credit platforms.

“[My customers] are angry when they learn that their 800 score that a [credit card company] quoted them is really only a 720 [from FICO],” she said.

While VantageScores are becoming more common, they’re still only a small part of the market. And, if you’re applying for a mortgage through a government-sponsored entity like Fannie Mae or Freddie Mac, you have to use FICO. They aren’t, under current law, allowed to use other scoring models to evaluate applicants. (There’s currently a bill in Congress, The Credit Score Competition Act, to allow them to do so.)

Like Ms. Haydon’s clients, at least a few consumers have reported in comments on Credit Karma’s own website that the score Credit Karma gave them was considerably higher than the FICO Score used by their banks.

Why is this bad? Because getting approved or getting the best interest rates often depends on meeting certain credit score thresholds. If the best rates require a credit score of 740, and you think your score is 760, you’re going to be really disappointed when your bank tells you it’s actually 730. Or, even worse, 690!

That’s why it’s extremely important to know your FICO Score, offered by Experian (with enrollment in Experian CreditWorksSM), rather than the credit scores offered by other competitors.

That’s why, if you’re really serious about buying a house or a new car, it’s important to keep an eye on your FICO Score (See FICO Score with enrollment in Experian CreditWorksSM).