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Scholar H-Index Calculator for Google Chrome and Firefox - Official documentation

How the Calculator works? I've installed it and I see no button!!

ANSWER: Point your browser to http://scholar.google.com and make a search. You will notice LOT of NEW STUFF.

You will be redirected to this very same page only on the first time you install the Calculator, or when an automatic upgrade has been installed. Apologies for this little bothering and have a look at the docs! (or maybe not).


Scholar H-Index Calculator (the Calculator from now on) is a bibliometric and citation analysis tool which works as an addon for Google Chrome (Firefox support has been discontinued). The Calculator enhances Google Scholar results pages by showing a number of bibliometric indicators computed using the data appearing on video as input. Once installed, the Calculator works transparently when querying Google Scholar: as soon as you make a query, result pages are enriched with a number of useful data (e.g. the h-index computed on the basis of displayed data), and new analysis functions are available.

The Calculator is fast and very responsive, as no external server is contacted. There is only interaction between your browser and the Google Scholar portal. No personal nor anonymous data about your activity on Google Scholar is collected.

How to use it

Starting using the Calculator is as easy as the following two steps:

  1. Download and install the Calculator using your web browser (Google Chrome is the only supported browser at the moment)

  2. Point your browser to Google Scholar and make a query! Once installed, the addon displays on top of Google Scholar result pages, the corresponding h-index, g-index, e-index and other measures of impact for the submitted query.


The Team

Project Coordinator

Developers Team (in no particular order)

Are you a research or industrial investor interested in financing the development of the Calculator? Do you need directions or have comments on the Calculator? You can contact us at shi_AT_mat.unical.it (replace _AT_ with a '@' to obtain our mail address).



The computed values are obtained from Google Scholar output (and from the Web) as it is, and might include self-citations, inaccuracies, informal and ghost citations. The author does not take any responsibility for the accuracy of indices values nor for the blind, non-manually-cleaned and inaccurate usage of this tool in official comparisons between authors and/or between journals.

You might be here because you are convinced that "high h-index = good scientist". Wrong. Have a look at this. If, on the other hand, you wrongly think that bibliometric analyses bring no information at all, read, e.g., this.

Advanced Interface

Since version 2.0 a new advanced interface mode can be enabled by clicking on the corresponding link located below the query textfield. Note that the addon advanced interface is not the same as the pre-existing Advanced Scholar Search link located at the right of the query textfield. When the Addon Advanced interface is enabled, a set of controls is visible per each paper. It is possible in turn:

  1. to select or deselect a single paper: deselected papers do not contribute in the computation of impact indices.

  2. to manually increase or decrease the number of self citations. Self citations are stripped from the total citation count of a given paper.

  3. to manually increase or decrease the number of authors for a given paper: this is useful when the number of authors reported by Google Scholar is not accurate and manual fixing is required (typical when the number of authors exceeds 4-5). Note: semi-automatic author fixing is possible since version 2.1 (see Section below).

  4. to load and save data: users can save their data analysis by simply saving the page at hand after completing their analysis.

Tips and description of impact indices

To have accurate results, set your Google Scholar preferences on the number of results to 100. In agreement with Google Scholar terms of service (which prohibits automatic querying), it is processed just the displayed result page. Since version 3.0, the Calculator can parse papers beyond the 100th by clicking on the two links on the sign Do you want to add '''more''' or '''all''' data?. More will trigger the addition of the next result page on the current page (and indices will be re-computed accordingly). When clicking on all, all the result pages, up to the 1000th paper (this is an intrinsic Google Scholar constraint) will be added and indices computed accordingly. In both cases you will see the added papers on the bottom of the page. If you aim at computing your own indices values accurately, I strongly suggest to use both the addon Advanced interface and the Advanced Scholar Search form already provided by Google Scholar. In the Advanced Scholar Search page, fill the Return articles written by.. field with the name at hand in quotes (e.g. "Giovambattista Ianni"). Also, in this same form, you might want to restrict search to the supposed field of experience. It is then possible to use the new Addon Advanced Interface (it can be activated looking below the query textfield) for performing fine-grained analysis (toggling papers on and off, etc.)

delta-H and delta-G

These two values measure the minimum number of citations needed for incrementing the current h-index (g-index, respectively), by 1. In the case of delta-h the value is computed as (h+1)-c[h+1] + sum_(from 1 to h)[max((h+1) - c[i],0)], where c[h] is the number of citations for the paper in position h, and h is the current h-index. delta-G is computed as (g+1)^2 - sum(from 1 to g+1)c[i], for g the current g-index. Note that for increasing h-index by 1, one has to obtain delta-H new citations on those particular papers which fail to have h+1 citations: all the first h+1 papers must reach at least h+1 citations. Usually, the (h+1)-th paper is the main culprit for the value of delta-H. Gaining a citation on a paper already having h+1 citations does not help in decreasing delta-H; viceversa, for increasing g-index, any new citation on the first g+1 papers matters, no matter how it is distributed.

delta-H and delta-G should be a measure of how difficult would be for the author at hand to increase his/her h and g-index. Note that the range of delta-h and delta-g is relatively small (in the worst scenario, delta-h-max= 2h+1 and delta-g-max=2g+1).

Normalized Values

Normalized values (the second row of data which is displayed) are computed by normalizing the number of citations found per each paper. From version 2.3 on, there are two types of normalization.

Normalization per author: if paper i has been cited t times, and has been written by k authors, its number of normalized citations is t/k. All the indices values, in the row where data are normalized per author, are computed considering these normalized values. In particular the normalized h-index corresponds to h_{I,Norm} of Publish or Perish. Due to limitations on the Google Scholar output format, Scholar H-Index truncates to 4 (or 5) the author count for papers having more than 4 authors. In such a case, the presented h_{I,Norm} has to be taken has an upper bound estimate of its real value (take care, especially for fields like Biology and Chemistry in which 12+ authors is the usual number). For having a finer-grained value the Addon Advanced Interface allows to semi-automatically fix the number of authors to the accurate value (see above).

Normalization per age: if paper i has been cited t times, and has been written in 2001, its number of normalized citations per age is t/(CY-2001+1), for CY the current year. The above corresponds to the contemporary h-index of Sidiropoulos et al., with parameters delta=1 and gamma=1. Note that indices (h,g and e) computed on values normalized per age do not coincide with any of the Age Weighted metrics displayed by Publish or Perish, nor with hc-index (which is the contemporary h-index with delta=1 and gamma=4).

Although this metric can be subject of criticism (values will abruptly change each Jan 1st 0:00:01; citations on old papers become exponentially less influential year by year), we found it as having an intuitive simmetry and interpretation, compared with plain indices, and compared with indices normalized per co-authorship.

Author lists refinement

This function allows to (semi)-automatically compute accurate normalized indices, overcoming the underestimate of 4 authors in case of multi-authored papers with 4+ co-authors. If Scholar Preferences are set to display Bibtex data URLs, the advanced interface displays a new control named Refine this author list per each paper. Given paper P, acting on its corresponding Refine this author list button will fill the P entry with its full list of authors, and displays the full name of the journal/conference of P (if data is available). Indices are automatically updated accordingly.

It is also available a button named Refine all bibliographic entries, which will automatically perform the abovementioned refinement per each displayed paper. Be warned that refining all papers implies heavy traffic from your browser to the Google Scholar portal, and might make Scholar detect you as an automated software, subsequently asking for a captcha.

Version 3.0: complete (aggressive) author list refinement

Google Scholar displays only some authors for a given paper P, and this affects the Calculator estimates on the number of authors. Since version 2.1, the Calculator can complete the list of all authors for P: this feature is called Author Refinement and uses BibTeX data (provided by Scholar). It works only if Scholar Preferences are set to display BibTeX data for the selected paper. Note that BibTeX data may be incomplete: in this case, BibTex author lists are terminated with the string "others" meaning that the list is incomplete.

Since the 3.0 Release, the Calculator implements a new system that aggressively completes the list of the authors. We can explain generally how the system acts: it downloads the Web page corresponding to the paper (whose link is provided by Scholar), reasons inductively on it and extracts the remaining authors initially not present. To use the new aggressive refinement system, just click on the button labeled Refine This Author List near each record on Scholar, as in previous versions.

We are currently measuring the precision and recall of the system, with accurate experiments. We can preliminarily say that the system works with a 100% rate precision in most cases. However, aggressive refinement is strongly based on the Web page referenced. This means that if the page does not actually lists the authors for a paper, it is corrupted, it is in PDF format (not supported yet), or it is temporarily unreachable on the Internet, the aggressive refinement system, of course, will not be able to extract accurate data and will report an error message.

Version 3.0: Custom formula editing

As of Calculator 3.0, there is the possibility for users to add their own bibliometric formulas and display their outcome next to default indices. There are two types of custom formulas: Normalizations and Indices. Custom formulas are visible only when the Advanced interface is enabled.


In the Calculator information box, each row shows bibliometric indices depending on a given Normalization. Each normalization weighs citations of each paper depending on a given criterion. Three are the default normalizations:

You can add your own normalization formulas by clicking on the button 'New normalization' on the bottom of the Information box. Two editable textfields will appear. Enter the normalization name in the leftmost field and your custom formulas in the rightmost. Click anywhere else when ready, and if your formula is correct, you should see a new row in which all the available indices are computed according to your new normalization notion. Enjoy!

Custom Normalization Formulas Language

You should be aware that normalization formulas are applied on per paper basis: your normalization formulas are intended to work in the context of a single paper. For a paper i a custom normalization formula f(i) returns a number of citations, depending on how f behaves. A normalization formula can access the following attributes of the paper i:

Allowed symbols:

==== Some further examples ====:


Indices correspond to columns in the Calculator information box. They correspond to a bibliometric index computed on the basis of a given set of papers. Besides the default indices you can add your own.

Custom index formulas Language

Differently from normalization formulas, indices formulas are applied on the current sorted list of papers (usually the list of entries displayed on video, sorted by the number of normalized citations at hand). The current list of papers can be changed either by a) making a new query, or b) telling the Calculator that you want to add more data to the current set, by clicking over the appropriate links presented by the Calculator. For a sorted set of papers S a custom index formula f(S) returns an index value, depending on how f behaves. An index formula can access the attributes of all the papers of the corpus. Per each row in the information box, the corresponding normalization function is applied beforehand, and papers on video are preliminarily sorted according to their number of normalized citations: then, f is computed per each row, according to the corresponding normalization and the obtained sorting. The language available for custom index formulas is much richer than the normalization language. Constructs available are listed next.

In the following, assume a sorted list of papers S, and a normalization function n(i), for i denoting the i-th paper of S are given.

Special arrays:

x can be any allowed formula.

Special symbols:


Aggregate functions are available: these come in two possible forms:




Where start and end are expressions denoting respectively the numeric range which variable will sweep on; variable is an identifier of choice, which is allowed to appear in expression. A booleanExpression is in the form expr relOp expr where relOp can be one among < (less than), > (greater than), >= (greater or equal than), <= (lesser than or equal),== or = (equal to), != or <> (different than).

Currently available aggregate functions are min, max, sum and prod. In order to exemplify how aggregates work, assume to have a set of 5 papers with respectively 10, 6, 4, 2 and 1 citations. Then

    min(1,N,i,citations[i]) = 1
    max(1,N,i,citations[i]) = 10
    sum(1,N,i,citations[i]) = 23

Boolean expressions can be used to select which papers should be filtered out in the aggregate function. For instance, the Google My Citations i10-index (the number of publications with at least 10 citations) is

   sum(1,N,i,citations[i] >= 10,1)

As in normalization formulas, allowed algebraic expressions include +, -, /, *, ^, (, ), with intuitive meaning.

Some examples

Indices used in the 2012 Italian "Abilitazione Scientifica Nazionale"

These can be programmed in the following way:


Here sum(1,N,i,citations[i]) is the total number of citations reported, while max(1,N,i,year[i]>1900,age[i]) estimates the academic age of an author as the age of the oldest paper appearing in the current set of papers. A paper is selected only if its year is greater than 1900 in order to exclude papers with unknown date from the computation.

Co-authors clustering (experimental)

Since version 4.0, the Calculator automatically groups papers based on their likelihood of being written by the same author. This helps in reconstructing author careers when homonymies come into play. You should see in the left pane a number of co-authors clusters, each of which associates a group of papers with a group of co-authors. Papers corresponding to a given cluster can be conveniently selected and de-selected by using the "Select/Deselect" Papers button.

How it works: at the moment, clusters are built by looking up author names which are in common between papers, and by looking at common keywords between paper titles. For instance, if paper P0 has been co-authored by authors A,B,C and paper P1 by authors D,C,B,K, P0 and P1 will be grouped in the same cluster since they share B and C as common authors (in order to be clustered together, two papers must share at least two authors). Papers are also clustered when they share at least two keywords in common, like in e.g. " Answer Set Programming: a Primer" and "A uniform integration of higher-order reasoning and external evaluations in answer set programming ".

We are working at improving our clustering algorithms, thus feedback is welcome!

Automatic Self-citation cleaning

As of Version 4.2, it is possible to clean each individual paper citation count from what are recognized as self-citations.

A paper S is considered a self-citation of P, if P and S share at least one author. Author matching is done by comparing Google Scholar unique author IDs. However, for authors not having a personal account on Google Scholar, self-citations are checked by comparison of the author's textual names, thus the cleaning process can be in principle affected by homonymies.

How it works: if the advanced interface is enabled, it is possible to clean the self-citations of a specific paper P by acting on the respective Clean citations button. This will sweep across the papers citing P and eliminate self-citations from the citation count of P. After the cleaning process is terminated, you should notice that the Invalid citations field in the P's record is incremented, while a label counting Valid citations appears close to the usual "Cited by" field. All the bibliometric indices are updated accordingly. The new feature is available on individual papers only and might result to be slow because of the necessary query Throttling.

Support for CiteseerX

Automatic index calculation when visiting CiteseerX has been discontinued since version 2.0.

Release Notes and history

Frequently asked questions

Why my h-index is not what I expect? Why displayed results are different by day/browser/language?

Computed indices values might differ from those of software tools like Publish or Perish mainly because Publish or Perish is hardwired to query http://scholar.google.com no matter which is your actual locale, while the H-Index Calculator works on the locale of your choice (scholar.google.it, scholar.google.co.uk etc.). Results from your local scholar.google.* might differ. Also note that queries submitted to Google Scholar such as author:"John Doe" return different (and tighter) results than author:John author:Doe, and also different from author:J author:Doe. Also you should take into consideration that selecting the field of expertise and narrowing your search with the filters available in the Scholar Advanced Interface will change indices values.

It is recommended, when collecting bibliometric data, to record:

Technical: for a sounder, uniform and comparable analysis, not a bad idea recording the whole content of the HTTP Requests sent, especially the User-Agent, Cookie, Host and Accept-Language fields.

Hello, I'm professor John Doe. Is there a chance I can tell my papers apart from all the other John Does in the academy?

The automated disambiguation of author homonymies is an hot research topic right now. You might want to give a try to the Author Cluster feature of the Calculator. This helps in grouping papers in clusters of authors which co-authored some paper together, and is usually very helpful in telling your past papers apart from your homonyms. Some manual adjustment might be needed.

Can I use the Calculator on keywords other than author names?

Yes, you can in principle measure the impact of technologies, scientific names, acronyms, journals and conferences using adequate keywords on Google Scholar and checking their impact using the Calculator.

Of course your research should be conducted with some care, since inaccuracies are behind the corner: a clear and unambiguous methodology should be set beforehand. E.g. it should be clearly defined how to treat synonimies like 'www' and 'world wide web', and where and when data is collected. Recall that Scholar data changes from locale to locale, and it is is continuously evolving over time.

"After about 50 searches (argh), I get the following 'friendly' message from Google: "We're sorry... ... but your computer or network may be sending automated queries"

This is not because of the presence of the extension in your browser. You must be aware that Google Scholar prevents massive querying on its servers. So, as soon as you perform massive activity, i.e. lot of queries in a very short time, no matter whether the Calculator is installed or not, you will get the above message. The Calculator has an internal query rate throttling mechanism which reduces the possibility of massive user activity: there are however some things you can do to further mitigate the issue. These are:

  1. Don't query quickly, the Scholar portal is not conceived for massive automated data collection activities, but for normal, human, users;

  2. Use wisely the function "add ALL the information". This function collects data from Scholar's additional pages by issuing for you 1 additional query for each additional page. For instance if you ask for the author name Carlo Rubbia, you will get 4740 results (as of Jan 2013), only 10 or 20 of which displayed by default. The feature "add ALL information" is capable to collect results up to the 1000th item, by issuing for you all the additional queries to the Scholar portal. This of course increments your traffic rate to and from Google Scholar servers. Use the function "add X results" instead. This latter adds only a limited number of results.

  3. Use wisely the feature "refine ALL bibliographic entries". Although this feature is very powerful and can complete partial co-author lists and partial paper information, you must be aware that the feature issues 1 additional query per paper (i.e. 100 queries on a page with 100 results), thus augmenting traffic to and from Google Scholar servers. Use the feature "Refine this author list" instead, which works on a single paper using just 1 additional query.

Can I quickly get back the access to Google Scholar once I'm blocked?

Usually it is sufficient to fill the CAPTCHA proposed by Google Scholar, or, when no captcha is shown, just wait a few minutes.

As of 2016 (one should assume that Google Bot Detectors will change their strategy over time), one can quickly regain access by either:

(Do these actions if you understand the technical implications of the above)

My search results in ">10" values, can I get a specific value instead of just ">10"

Yes, just add more results to the displayed page acting on the links appearing in the text which look like Want to add *10*, *100* or all results ?. We are sorry of not displaying 100 results by default, but this is due to the recent Google Scholar policy change (not the Calculator) of allowing maximum 10 or 20 results per query.

I'm getting a 'Error: document.getElementById(...) is null' error when running the addon

You're most probably running an obsolete version of the addon, most likely under Mozilla Firefox. You should switch to the Chrome version.

How can I remove the Calculator?

You can temporarily disable the Calculator by acting on the 'disable' toggle which appears right on top of the Calculator information box. For permanent removal:

Which permissions the Calculator asks for and why?

The Calculator asks for:

How can I cite the Calculator on my scientific publication?

You can use the following: Ianni, G. et al. (2010) Scholar H-Index Calculator, available from https://www.mat.unical.it/ianni/wiki/ScholarHIndexCalculator


mwiki: ScholarHIndexCalculator (last edited 2017-07-20 08:54:38 by GiovambattistaIanni)