FICO score is a credit scoring system that was developed in the1950s by Fair Isaac & Co. Today, the three major credit reporting bureaus Experian, Equifax and Trans Union all use FICO scores to evaluate the credit worthiness of almost 90% of the adult Americans. FICO scores can range from 300-850 and these scores are calculated on the basis of scoring models and mathematical calculations that are not revealed to the public. » Read more: Understanding What is a Fico Score and Tips on Hiring the Best Credit Repair Service