A friend and I have published one journal paper and one conference paper on the same topic. As I have seen we have made a some mistake in not adding the desired changes to the journal version of that paper based on the below rule (journal version needs at least 30% change):

So, it is okay to develop a previously published conference paper into a full-length manuscript and publish it in a journal later on. This is an acceptable practice, provided you clearly disclose the conference paper and include at least 30% new material in the journal paper

I have seen two papers of someone of our previous university, one conference and one journal paper with very similar titles (paper 1, paper 2). If possible I want to find a website that automatically checks the plagiarism percentage of academic papers, ideally without the need for the actual PDF versions of the papers (which are often paywalled).

  • What do you mean by "plagiarism percentage"?
    – GoodDeeds
    Commented Jun 20, 2021 at 20:16
  • 1
    Your question makes little sense. Any percentage value that some plagiarism checkers give is irrelevant and only used as a guideline for which papers to have a close look at. If you now know that your submitted journal paper does not meet the requirements, you should retract the submission while apologizing. In this way, you can fix your mistake by updating your paper and then submitting it elsewhere sooner (no need to wait for a rejection), without risking that the journal calls you out for your rule violation.
    – DCTLib
    Commented Jun 20, 2021 at 20:17
  • @DCTLib The way I read OP's question, it's not a merely submitted journal paper, it's one that was already published some years ago. Commented Jun 22, 2021 at 10:39
  • Thanks, @Daniel_Hatton, I don't get what is the meaning of OP's Question? I googled it but don't get what is the means of original poster's question means right now?! Commented Jun 23, 2021 at 8:52
  • @SoheilPaper the term OP is referring to you, so "OP's question" is your question
    – Christian
    Commented May 22 at 12:08

1 Answer 1


I doubt that any plagiarism checker will help you here. First, the 30% rule is not a standard measure, and it is difficult to judge in any case. While it may be a standard for some journal, it isn't 30% of the "words" that is important, but that the new work adds new "ideas" and/or "results" that an editor or reviewer would judge to be about 1/3 of the original.

Plagiarism checkers are very poor tools and are better for checking pure "copying" than for judging advances in scholarship.

Moreover, the journal version will probably have a longer "time in process" than the conference version, permitting you to make changes if the reviewers have issues.

But, ask yourself, what is "new" in the journal version - ideas and results mostly.

Note that it is possible to plagiarize using none of the original results, simply by paraphrasing the old work without citation. It is the lack of citation that makes in plagiarism, though over-copying can be a different, but still important, offense, perhaps copyright violation.

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