Your credit score is the only crucial piece of information left out of your credit reports, including your free yearly credit reports.

Your credit score is a number between 300 and 850 that represents to lenders your financial trustworthiness. Your credit score is based on a combination of factors, some of which may surprise you, that we've conveniently laid out for you below.

Here's how your credit score is calculated:

All three of the major credit bureaus—Experian, Callcredit, and Equifax Credit Bureaus—calculate your credit score separately, though their individual systems for calculating your credit score are all mutually based on the same method.

Obtaining not just your credit report, but also your credit score is especially important if you're applying for a mortgage, as 75% of mortgage decisions are based on your credit score.

Interestingly enough, you can purchase your credit score through the Equifax Credit Agency (but not at all from either of the other two). If you're in the middle of obtaining your free yearly credit report from Equifax, you will be given the option to buy your credit score as an add-on.