An overview of source normalized impact per paper (SNIP)

Source normalized impact per paper (SNIP) is a sophisticated metric designed to measure the contextual citation impact of academic journals. Developed by the Centre for Science and Technology Studies (CWTS) at Leiden University, SNIP provides a different perspective on journal impact by accounting for differences in citation practices across different scientific fields. The following is a detailed explanation of what SNIP is, how it works, and its significance in the academic community.

What is SNIP?

SNIP is a metric that reflects the contextual impact of journal citations. SNIP considers citation behavior that is specific to its subject area. This means that SNIP adapts to various citation norms across disciplines, allowing for more accurate and fair comparisons between journals in different fields.

How is SNIP calculated?

Calculating SNIP involves several steps to ensure that SNIP accurately reflects the impact of citations in the context of a particular field:

  1. Raw impact per paper (RIP): the average number of citations received per paper published in a journal is calculated. This is similar to basic citation averaging.
  2. Database citation potential (DCP): DCP measures the citation potential within a specific field. It is the average number of citations received by papers in that field, reflecting how often papers are typically cited in that field.
  3. SNIP calculation: The SNIP is then calculated by dividing the RIP by the DCP. This normalizes the citation impact by taking into account common citation practices in the journal’s subject field:

The SNIP score is the ratio of a source’s average citation count and citation potential. Citation potential is measured as the number of citations a journal is expected to receive for its subject area. The longer the reference list of a citing publication, the lower the value of the citations coming from that publication. Therefore, SNIP allows direct comparison between research fields with different publications and citation practices. SNIP is calculated as the number of citations given in the current year to publications in the last three years divided by the total number of publications in the last three years. Journals with an SNIP of 1.0 have the median (not average) number of citations for journals in that field.

Why is SNIP important?

SNIP offers several key advantages and plays an important role in the evaluation of academic journals. Normalized impact on the field, by adjusting for differences in citation practices, SNIP provides a fairer comparison of journals in different scientific fields. This is particularly important in multidisciplinary research. In addition, researchers can also use SNIP to identify high-impact journals in a particular field, guiding their publication strategy and ensuring their work reaches the right audience.


SNIP is a valuable metric for assessing the citation impact of academic journals in a way that accounts for differences in citation practices across fields. By normalizing these differences, SNIP allows for more accurate and fair comparisons between journals, helping researchers and institutions in their decision-making process.

By: I. Busthomi