In United States of America, the creditworthiness of a person in established with the help of his credit score. This number is assigned to an individual by FICO, a pioneer organization in credit scoring since 1958. FICO assesses the credit history of the person by evaluating the credit reports generated by three fundamental credit bureaus in the US namely, Equifax, Experian and TransUnion. Each of these credit bureaus have their own database, where they store credit history of a person. However, there is no uniformity regarding the reports generated by these bureaus, meaning they may have different information about the credit history of a same person. As a result, the person may have three different credit scores, with significant variations. These credit scores are referred by almost all credit institutions whenever there is an application for credit by a person. Credit score estimator is a software that generates credit score on the basis of available credit history. Credit Score Estimator FICO (Fair Isaac Corporation) software analyzes the statistical data available to it and comes up with a credit score for a person. FICO has its own parameters against which the credit history of a person is checked. It is a software program which automatically generates the credit score of the person on the basis of a formula devised by FICO. The credit score range lies between 300 to 850 points. This software is used by the three credit bureaus mentioned above to generate their respective scores. The credit bureaus then sell the scores to the lenders or credit institutions. US citizens can legitimately obtain their credit report from their website. Annual credit report once a year can be obtained, free of charge. Credit score information can be obtained from credit reporting agencies at an additional fee. You can also buy your credit score directly from FICO, which calculates them using data from Equifax and TransUnion. If you are particularly interested in credit score estimation for free then, you may visit various sites available on the net which offer a free credit score calculator. These websites present you with a questionnaire based on your credit information. They have their own formulas to calculate the credit score. The scores are also available on their website 'myFICO' which can give you a correct estimate of your FICO score, though not for free. Equifax credit reports and a scoring equation is used by myFICO's ScoreWatch to generate FICO scores, whereas myFICO's Credit Estimator does not use any data for calculating FICO score. It is entirely calculated based on the user's answers to the questionnaire. Bankrate credit score estimator is yet another tool, which is similar to myFICO's Credit Estimator and finds credit score depending upon the user's answers to their 12 question credit questionnaire. CreditKarma is another credit monitoring service, which uses TranUnion data to find your credit score. How Accurate are Credit Score Estimators Credit score estimators are only programmed to give you a rough estimate about your credit score. Sometimes, they may vary by as high as 50 points from the actual score. A deviation of 50 points may force you to mistake your prospects of getting credit. Most importantly, your lenders are not going to get your credit scores from any of the estimators. Hence, it would absolutely make no sense for you to refer to any source of credit score information which your lenders do not trust. Lenders will be getting your credit score from the three most trusted credit bureaus mentioned above. In the nutshell, credit estimators are good for you, only if you casually want to check your score. If you are seriously evaluating your prospects of getting credit, then you would better trust the authorized credit score monitoring services. You can get your actual FICO score at USD 20 to USD 30 from myFICO. A 30 days trial pack is available which you can cancel later. However, before you sign up for any legitimate or otherwise credit score estimator services, you should first obtain your credit report from annualcreditreport.com. Oftentimes, there may be some errors in your credit report, which may need fixing.