Enter the number of citations a publication received in the current year, the number of total citable publications in the previous year, and the number of citable publications in 2 years prior. The calculator will evaluate and display the impact factor.

Impact Factor Formula

The following formula is used to calculate a journal impact factor.

IF = Cy / (Py-1 + Py-2) 
  • Where IF is the impact factor
  • Cy is the total number of citations in the current year
  • Py-1 is the total amount of citable publications in the previous year
  • Py-2 is the total amount of citable publications in the year 2 years before the current year

Impact Factor Definition

What is an impact factor? An impact factor, also known as a journal impact factor is a measure of the relative importance of an academic journal that is based on the number of citations the journal receives relative to the number of publications it published in the previous two years.

Example Problem

How to calculate impact factor?

  1. First, determine the number of citations.

    For this example, the journal we are analyzing received 3,567 citations for the current year.

  2. Next, determine the number of publications in the two previous years.

    In the previous year, the journal published 400 publications, the year prior to that it published 600 citable publications.

  3. Finally, calculate the impact factor.

    Using the formula above, we find the impact factor of our journal to be: IF = (3,567)/(400+600) = 3.567.


What is good impact factor of a journal? An impact factor can be used to calculate the relative importance of a journal based on citations, therefore, a higher impact factor means the journal is more reputable. Most journals should try to achieve impact factors of great than 25.

What are high impact factor journals? Some of the top impact factor journals include but are not limited to: CA-A Cancer Journal For Clinicians, New England Journal of Medicine, Nature Review Drug Discovery, Chemical Review, Lancet, Nature Reviews Molecular Cell Biology, Nature Biotechnology, Nature Material, Science, CELL.

Why impact factor is important? A journal impact factor is an important base metric in determining the reputation of a journal. It does not mean that you should only trust journals with high impact factors, but rather that other scientists trust those particular journals the most, and want to have their publications published in those journals.