Your FICO Scores are based on five main factors. Payment history: Your payment history accounts for 35% of your FICO Score, the largest share. It's your track record of making payments on credit cards and loans. Paying all your bills on time is one of the best ways to improve your credit scores. Credit utilization: This accounts for about 30% of your FICO Score. It's based on how much of the available credit on revolving credit lines, primarily credit cards, you're using. Experts say it's best to use no more than 30% of your credit at any point in the month, and for the best scores, stay under 6%. Calculate your credit utilization rate by dividing your total outstanding credit card balances by your total credit limits. Length of credit history: This accounts for about 15% of your FICO Score. It refers to the amount of time you have had credit accounts open, and how recently you've used an account. A longer history is a plus. Credit mix: Your credit mix makes up about 10% of your FICO Score. Credit mix means having different types of credit accounts, such as credit cards, a car loan and a mortgage. Having a wide range of accounts plays a small role in determining your FICO Scores.