Impact factor, quartiles and h-index, explained

The metrics at a glance

One idea clears most of the confusion, so keep it in mind first. Every journal metric belongs to a database. Only journals in Clarivate’s Web of Science Core Collection can get a Journal Impact Factor. CiteScore, SJR and SNIP are there only for journals in Scopus. A journal that is not in the database cannot have that metric, whatever its website is claiming.

Journal Impact Factor (Clarivate)

Clarivate publishes the Journal Impact Factor once every year, in June, in its Journal Citation Reports (JCR). The calculation is as below.

Citations received in year Y to items the journal published in years Y−1 and Y−2, divided by the number of citable items (articles and reviews) the journal published in Y−1 and Y−2.

Suppose a journal has a JIF of 3.0. On average, its recent articles and reviews got about three citations each in the year measured. It is only an average, and citations are very uneven. A few heavily cited papers can carry a journal’s JIF, while most of its other papers get far fewer citations.

Changes worth knowing about

• From the 2023 JCR release onwards, Clarivate gives a JIF to every journal in the Web of Science Core Collection that meets its criteria. This covers the Arts & Humanities Citation Index and the Emerging Sources Citation Index (ESCI) also. Till then, ESCI journals did not have any JIF. Old university rules which equate “has an impact factor” with “is in SCIE or SSCI” are now out of date on this point.
• In the same release Clarivate started showing JIF to one decimal place instead of three. The idea is to stop people from comparing journals on very tiny differences.
• Clarivate also brings out the Journal Citation Indicator. It is normalised for field, so it helps when you want to compare journals from different disciplines.

JCR quartiles

In every Web of Science subject category, journals are ranked by JIF and the list is cut into four equal parts. The top 25% is Q1. If a journal is listed in two categories, it can be Q1 in one category and Q2 in the other.

CiteScore (Scopus)

CiteScore is the journal metric of Elsevier, worked out from Scopus data. After its 2020 methodology revision it uses a four-year window. Take CiteScore 2024 as an example. It counts citations received in 2021–2024 to documents published in 2021–2024. Then that total is divided by the number of those same documents.

Five document types are counted, namely articles, reviews, conference papers, book chapters and data papers. Scopus counts these five in the numerator and in the denominator both, so there is no mismatch.

• Annual value: comes out once a year, and after that it does not change.
• CiteScore Tracker: a running estimate for the current year, updated every month. See it for the trend only, and in your file give the annual value.
• Percentile and rank: on Scopus Sources you can see the journal’s rank in each of its subject areas. When somebody says “Scopus Q1”, mostly they mean the top quarter by CiteScore percentile.

You can see CiteScore free of cost on Scopus Sources. To find a journal there with its ISSN, follow our Scopus guide.

SJR, SNIP and why “Q1” means different things

SJR (SCImago Journal Rank)

SCImago calculates SJR from Scopus data. In SJR each citation gets a weight based on the prestige of the citing journal, somewhat like how PageRank gives weight to links. It takes citations in one year to documents published in the previous three years. SJR is free on the SCImago Journal & Country Rank website. For most Indian scholars, this website is the first place where they see the familiar coloured Q1–Q4 quartile badges.

SNIP (Source Normalised Impact per Paper)

SNIP is made by the Centre for Science and Technology Studies (CWTS) at Leiden University, and it also runs on Scopus data. Some fields cite much more than other fields. SNIP corrects for this, so one citation in a field where citations are few carries more weight. To compare, say, a mathematics journal with a biomedical one, SNIP is more useful than a raw citation average.

Why “Q1” is ambiguous

These rankings are built on different databases and different formulas, and their category schemes also differ. Because of that, the same journal can legitimately be Q1 in SCImago and Q2 in JCR, or the reverse way. When your university or funder asks for a particular quartile, ask them which source and which year they mean. Keep a dated screenshot as proof at the time of submission.

How to check a journal’s quartile in SJR and JCR, step by step

In SCImago (free)

1. 1

   Search the journal on scimagojr.com

   Type the ISSN in the search box on the home page. Searching by title also works, but with the ISSN you avoid look-alike journals.

2. 2

   Confirm it is the right journal

   On the journal page, first check the ISSN, the publisher and the coverage years. Read the numbers only after that.

3. 3

   Read the subject categories

   The Subject Area and Category box shows all the categories in which SCImago ranks this journal. The quartile is worked out separately for each category.

4. 4

   Find the Quartiles chart

   Scroll down to the Quartiles chart. It shows every category year by year in colours, green for Q1, yellow for Q2, orange for Q3 and red for Q4. Go along the row of your category till the year you need.

5. 5

   Take a dated screenshot

   Take a screenshot of the chart with the category names showing, and write down the date. When SCImago releases a new year’s data, the figures will change.

In Journal Citation Reports (through your library)

JCR needs a subscription, so open it through your university library. Search the journal by its title or ISSN and go to its profile. There you will find every Web of Science category the journal is listed in. For each category the profile gives the rank by Journal Impact Factor and the quartile, and you can go back to earlier years also. Clarivate is changing the page layout from time to time, and a senior’s old screenshot can have other labels. If your library does not have JCR access, ask guide or the research cell how the university wants the impact factor to be shown as evidence.

Which quartile do you report?

One journal listed in three categories can have three quartiles, and each of them can change every year. Many scholars are quoting the best one only, without mentioning about the other categories.

• When your university rule names a source, follow that source only. VTU’s thesis checklist is one example. For recent batches it asks for a Q1 to Q3 Scopus journal. But it does not say if it means the SJR quartile or the CiteScore percentile that Scopus itself shows. In such a case, ask the research section which one they accept (the detail is there in our guide to PhD publication requirements).
• When the rule names a year, use that year. If the rule says nothing on the year, mostly people take the latest year available on the day they submit, but confirm once with the research cell.
• Sometimes the journal’s quartile differs from one category to another. Then report the category that is closest to the subject of your paper, and write the category name with it.

In the CV or pre-submission file, write the full detail, for example “Q2, Economics and Econometrics, SJR 2024”. A doubtful DC member can check that on SCImago. With just “Q1 journal” they have nothing to check. Either way keep the dated screenshot in your file.

The h-index: a researcher metric, not a journal metric

The physicist Jorge Hirsch proposed the h-index in 2005, and it is a measure for one researcher. Your h-index is h when h of your papers have got at least h citations each. Say your h-index is 8. Then eight of your papers have got eight or more citations each.

Why your h-index differs between services

• Google Scholar counts citations from whatever it can find on the web. That means journals, but also theses, preprints, conference papers, reports and sometimes duplicates. Usually it gives the highest number of the three. You maintain the profile yourself. Scholar shows one all-time value and one recent value (last five years), along with the i10-index, which means papers with ten or more citations.
• Scopus takes only those citations that come from documents indexed in Scopus, and it makes the author profiles by itself. Sometimes a profile gets split wrongly, or two profiles get merged wrongly. Till that is corrected, the number can be off.
• Web of Science counts citations only inside the Web of Science Core Collection. Many times this is the most conservative figure.

No single one of these is “the real” h-index. So when you put it anywhere, write the service and the date next to it. For a scholar who is early in the career, the h-index does not say much to anyone. It grows with the length of a career, and it varies hugely from field to field.

Unofficial metrics to set aside

Any number that calls itself an impact factor but is not Clarivate’s JIF is not an official metric, and you can leave it aside. Some names you will see a lot on journal websites are these.

• “Global Impact Factor”, “Universal Impact Factor”, “International Impact Factor”
• “SJIF” or “Scientific Journal Impact Factor”, and “Cosmos Impact Factor”
• “Index Copernicus Value (ICV)”, which is a score from a commercial database. It is not an impact factor, and Clarivate and Scopus do not recognise it
• “ISI indexed”, where the ISI is some unrelated organisation using the old name of Clarivate’s predecessor

You can test any such number yourself. A genuine JIF will be there in JCR. A genuine CiteScore, SJR or SNIP will be there on Scopus Sources or on SCImago. If the number is not found in these places, it is not an official metric. For the other warning signs to check along with these numbers, see our predatory journal guide.

Using metrics sensibly when choosing a journal

• Compare journals inside one field only. In mathematics a JIF of 2 may be excellent, while in cell biology the same 2 is only modest.
• See the trend over some years. Sometimes a journal’s metrics jump sharply in single year, together with a sudden rise in the number of papers it publishes. Check such a journal carefully before you send your paper there.
• The journal’s number does not tell anything about your own paper. Plenty of papers in high-JIF journals hardly get cited, and many important papers come out in modest journals. The San Francisco Declaration on Research Assessment (DORA) also says the same thing, that journal-based metrics should not be used for judging one article or one researcher.
• Go for the journal where your paper actually fits. If you aim a paper at a journal a little above its level, it is likely to get desk-rejected and you lose weeks. A well-matched Q2 journal that publishes your type of work is many times the quicker and surer route.
• Find out what your institution actually asks for. UGC’s 2025 suggestive parameters for judging journals have impact factor and CiteScore in the list, with many other criteria. But the decision on what counts is with your university. See our UGC-CARE guide.