What does it measure?
The Impact Factor measures the number of citations received by a journal.
How is it measured?
The Impact Factor is calculated by dividing the number of citations to a journal by the number of articles published in the journal. For example, the 2012 Impact Factor is calculated by taking the number of citations in 2012 to articles published in the same journal in 2010-2011 divided by the number of articles published by the journal in 2010-2011.
The equation looks like this:
= Impact Factor for journal
Number of items published 2010-2011
How do I get the data?
Go to the Databases A to Z list and click on the link to Journal Citation Reports (Thomson Reuters).
Select either the JCR Science or JCR Social Sciences Edition and choose the year.
You are given the option to search for a specific journal, view a list of all journals, or view a list of journals by subject, publisher, or country.
The results page will display a table of data with the Impact Factor and other impact metrics. Click on the journal’s title to view more information about the journal and additional citation data. By default, a results list with multiple journals will display alphabetically by title. You can use the drop down menu at the top to sort by Impact Factor, or by another metric.
Garfield, E. The Thomson Reuters Impact Factor. Retrieved from: http://wokinfo.com/essays/impact-factor/