Direct answer
A QuillBot similarity index is a percentage showing how much of your text matched sources in QuillBot's own comparison index, not a Turnitin score and not a verdict on your work [1]. The number only becomes meaningful when you open the matched sources and read them one by one, because a 30% index built from correctly cited quotations is a very different document from a 30% index built from copied paragraphs [2]. Two checkers can return two different percentages for the same file, and neither number transfers to the other tool [3].
What Does the Similarity Index in QuillBot's Checker Actually Measure?
The similarity index is a coverage measurement, not an integrity judgment. It reports the share of your submitted text that the checker was able to match against items in its source index, and it presents those matches as a list you are expected to review [1]. Nothing in the calculation distinguishes between a block quotation you attributed properly and a paragraph you lifted without a citation, so the percentage on its own carries no verdict [1].
That is why the matched-source list matters more than the headline figure. A writer who sees 18% should open every match and ask three questions: is this my own citation, is this a common phrase or reference, and is this a genuine unattributed overlap [2]. Turnitin gives instructors the same instruction for its own Similarity Report, warning explicitly that a high percentage is not proof of plagiarism and a low percentage is not proof of originality [2].
The filters and exclusions a tool applies also shape the number you see. When a checker strips bibliography and quoted material before comparing, your index drops; when it leaves them in, the same essay scores higher [2]. Turnitin's own report lets the reader toggle those exclusions, which means even within one system a single paper can display several different percentages [2].
Finally, treat the index as a diagnostic that points you toward a passage, not as a grade. If a match turns out to be your own earlier draft, a standard definition, or a properly block-quoted source, the index did its job by surfacing it for review [1]. If it turns out to be unattributed prose, you have found the exact sentence to rewrite or cite before anyone else reads it [2].
Is a QuillBot Similarity Score the Same as a Turnitin Similarity Score?
No, and the difference is structural rather than cosmetic. Each checker compares your file against its own database, and because those databases are built from different collections, the same document produces different percentages in each tool [3]. Turnitin compares against its repository of previously submitted student papers, academic journals, and web content, which is a materially wider and differently weighted corpus than a general-purpose writing tool maintains [3].
The most consequential gap is the student-paper repository. A checker that does not hold a large archive of essays submitted at universities will systematically under-report matches to other students' work, so a comfortable-looking score can hide the overlap that matters most in an academic misconduct review [3]. Turnitin's index exists precisely because that overlap is what institutions are looking for [3].
There is also a second report that a similarity index never shows you. Turnitin produces an AI Writing Report as a separate document from the Similarity Report, with its own percentage and its own segment-by-segment breakdown of which passages were flagged [4]. A similarity checker answering "how much of this matches a source" tells you nothing about "how much of this reads as machine-generated," and those are two independent questions [4].
Because scores are not portable between tools, you cannot convert a QuillBot index into an expected Turnitin figure with any arithmetic [3]. The only reliable way to know what an institution will see is to look at a report produced by the same detection system the institution uses [4].
How Can You Verify Your Real Turnitin Similarity and AI Score Before Submitting?
Students normally encounter these reports only after the fact, inside the institution's learning management system, which is too late to act on them [4]. A pre-submission check closes that gap by generating the same two documents — a similarity report and an AI writing report — on your draft while you can still edit it [4].
When you read the AI side, expect a specific display convention: Turnitin shows an asterisk (*%) instead of an exact percentage when the AI score falls below its 20% confidence threshold, because those signals are low-confidence rather than clean [4]. Seeing *% is therefore not the same as seeing 0%, and it is worth understanding before you interpret your own result [4].
On the similarity side, work through the matches rather than fixating on the total. Turnitin's guidance to instructors is to interpret each match in context and to weigh source type, quotation practice, and citation quality over the raw number [2]. Applying that same discipline to your own draft is the single most useful habit you can build before submission [2].
Two practical details make a preview genuinely useful: the check should not deposit your file into a student-paper repository, and it should return the report fast enough to matter before a deadline [4]. Those are the conditions under which a pre-submission report behaves like a dry run instead of a permanent record [4].
Reading a percentage is only half the job — the useful part is seeing the report the way your marker will see it, with every matched source and every flagged segment laid out side by side. That is exactly what turnitin0 produces: an actual Turnitin AI detection report and an actual similarity report, generated from your own draft before you submit it, so you can compare the flags against your citations while you still have time to fix them.
※ Turnitin0.com - Actual Turnitin AI Report Cover, Score, Flag And Similarity Summary
FAQ
Does a high similarity index mean I will be accused of plagiarism?
No. Turnitin tells instructors directly that a high similarity score is not proof of plagiarism, and the same logic applies to any index — the matches have to be read in context [2]. A high number built from cited quotations and standard definitions is usually defensible.
Why is my QuillBot similarity index lower than my friend's Turnitin score for the same essay?
The two tools compare against different databases, so identical text yields different percentages [3]. A checker without a large student-paper archive will typically miss overlaps with other students' essays, which pulls its number down [3].
Can I convert a QuillBot percentage into an expected Turnitin percentage?
There is no reliable conversion. Scores are not transferable between checkers because each one's index is built differently, so a ratio between them is not a stable property of your text [3].
Does a similarity checker also tell me my AI score?
Usually not. Turnitin's AI Writing Report is a separate document from the Similarity Report, with its own percentage and segment breakdown [4]. If you need both signals, you need a check that returns both reports.
What does an asterisk next to a Turnitin AI score mean?
It means the AI score fell below Turnitin's 20% confidence threshold, so the system displays *% instead of an exact figure [4]. It signals a low-confidence result rather than a confirmed zero.