The credit score is calculated by many different factors.
The FICO credit scoring system (which is the most common credit score used) is as follows:
Credit history 15%
Payment history 35%
Amounts owed 30%
New credit 10%
Types of credit used 10%
This scoring system is reliable because these factors are the most relevant to whether or not you are a risky borrower. Remember, your credit score helps to determine if you will be approved for a loan or line of credit and what type of interest rate you will receive on the loan.