How to calculate Impact Factor of a Journal

[Gulshan Kumar Pahwa]

Please inform me how we can calculate the impact factor of a journal in very simple manner.
What is the formula for the same.

[saba nasreen bano]

Impact factor is given by Eugene garfield
it is a measure of the frequency with which the "average article" in a journal has been cited in a given period of time.

The impact factor for a journal is calculated based on a three-year period, and can be considered to be the average number of times published papers are cited up to two years after publication. For example, the impact factor 2010 for a journal would be calculated as follows:

A = the number of times articles published in 2008-9 were cited in indexed journals during 2010

B = the number of articles, reviews, proceedings or notes published in 2008-2009

impact factor 2010 = A/B

(note that the impact factor 2009 will be actually published in 2010, because it could not be calculated until all of the 2009 publications had been received. Impact factor 2010 will be published in 2011)

saba nasreen