Direct answer
Grammarly's AI detector and Turnitin's AI writing detector are two separate systems that frequently disagree, because they use different models, different training data, and different reporting contexts. Grammarly returns a percentage estimate for text you paste into its own product and reports to no one; Turnitin runs inside your institution's assignment workflow and produces the AI writing report your instructor actually reads [1]. A "human" verdict from Grammarly is therefore not evidence that your draft will pass a Turnitin check, and the reverse is equally true.
Does Grammarly's AI detector give the same result as Turnitin's AI writing detector?
No. The two tools answer different questions in different environments, and neither one is a substitute for the other. Grammarly's detector is a proprietary classifier that estimates how much of a pasted passage looks machine-generated, and Grammarly positions it as a writing aid rather than an academic-integrity ruling [1]. Turnitin's AI writing detection, by contrast, is generated inside the institutional integration and delivered as a distinct AI writing report alongside the similarity report [2]. Because the outputs are produced by unrelated models on unrelated infrastructure, matching percentages between them would be a coincidence rather than an expectation.
Turnitin is also explicit about the epistemic limits of its own output, which is a detail students rarely hear. Its guidance states that a high AI score is not proof of misconduct and a low score is not proof of authorship, and that results require human interpretation by the instructor [2]. That framing matters when you are comparing tools: if the institutional detector itself refuses to treat its number as a verdict, a third-party detector's number carries even less institutional weight.
There is a display convention worth knowing before you panic at a screenshot. When Turnitin's AI detection falls below its 20% confidence threshold, the report shows *% instead of an exact percentage, signalling a low-confidence signal rather than a precise measurement [2]. Students who see *% and assume they scored zero — or who see a Grammarly figure and assume it maps onto that band — are misreading both reports.
The practical takeaway is that Grammarly is useful for catching awkward phrasing and mechanical errors, but it is the wrong instrument for predicting an institutional outcome [1][2]. If the decision that matters is made by your instructor's Turnitin report, only a report in that format tells you anything actionable.
Can Turnitin detect text that Grammarly has rewritten or polished?
Yes, it can — and the reason is structural rather than a matter of how aggressive the rewrite was. Turnitin's AI writing report highlights flagged segments at sentence level, so a draft that was partly drafted by AI and partly polished by a grammar tool typically shows partial highlighting rather than an all-or-nothing score [3]. There is no "Grammarly mode" that switches detection off; the report simply reflects the statistical patterns of the text as submitted.
Detection is also editor-agnostic. The system evaluates the submitted text itself and has no visibility into which grammar checker, paraphraser, or assistant touched the draft along the way [3]. That means the common student assumption — "I only ran it through Grammarly, so it's my writing now" — does not translate into a lower score, because the classifier never saw the intermediate steps.
Because scoring is segment-level, mixed human/AI drafts land anywhere on the scale, and light polishing does not guarantee a comfortable result [3]. A hand-written essay with a few AI-assisted paragraphs can score meaningfully higher than the student expects, while a heavily edited AI draft can score lower. The only way to know which side of that line your draft falls on is to measure it rather than guess.
This is also why rewriting for the sake of sounding different is a weak strategy. Surface synonym swaps and sentence reshuffling change the prose without reliably changing the underlying patterns the detector responds to [3]. Substantive revision — restructuring arguments, adding your own evidence and analysis — is both better writing and a more defensible position if your instructor asks about the draft.
How can I check my own draft against the real Turnitin AI detector before I submit?
You cannot generate an institutional AI writing report yourself, which is precisely why pre-submission checking exists. Turnitin's own help documentation confirms that students generally do not have access to run their paper through the institutional integration; the AI writing report is surfaced to the instructor through the LMS assignment [4]. So the report that decides your outcome is, by design, one you only see after the fact.
A second complication is that results depend on the settings your instructor selected for the assignment [4]. Similarity and AI outputs can vary by course configuration, so a friend's report from a different module is not a reliable benchmark for yours. Any honest preview has to reproduce the report format and configuration the instructor actually sees, not a generic percentage.
That is the gap a pre-submission check fills: upload your draft, receive the AI detection PDF and the similarity PDF in the same format your instructor views, and read the flagging at segment level so you know which paragraphs to revise [4]. Doing this before the deadline converts an anxious guess into a concrete editing list, and it removes the temptation to trust a detector that has no connection to your institution.
If you are weighing whether to check at all, consider the asymmetry of the two errors. Submitting blind risks an unexplained high score you cannot contest; checking costs a few minutes and gives you the specific sentences to fix [4]. For a draft you have already run through Grammarly, that difference is the whole point.
Reading a Grammarly percentage tells you what one unrelated classifier thinks of a pasted paragraph — it tells you nothing about the report sitting in your instructor's gradebook. turnitin0 closes that gap by returning the actual Turnitin AI detection report and similarity report for your own draft, in the same format your professor opens, without adding your file to the student paper repository. Students upload a .docx, .pdf, or .txt file (English, over 300 words), and most orders are delivered in under 15 minutes, so there is still time to revise the flagged paragraphs rather than hope.
※ Turnitin0.com - Actual Turnitin AI Report Cover, Score, Flag And Similarity Summary
FAQ
Is Grammarly's AI detector the same as Turnitin's?
No. They are separate proprietary systems with different training data and different reporting environments; Grammarly's result is produced for the writer, while Turnitin's AI writing report is generated inside the institutional assignment workflow [1][2].
Does Grammarly make my writing look AI-generated to Turnitin?
Not automatically, but it does not protect you either. Turnitin evaluates the text as submitted and highlights flagged segments at sentence level, without any awareness of which editor was used [3].
What does *% mean on a Turnitin AI report?
It indicates that AI detection fell below Turnitin's 20% confidence threshold, so the report shows a low-confidence signal instead of an exact percentage [2]. It is not the same as a measured 0%.
Can I run my own paper through Turnitin before submitting?
Students generally cannot generate an institutional AI writing report themselves, because it is delivered to the instructor through the LMS [4]. Pre-submission checking services reproduce that report format for your own draft instead.
If Grammarly says my text is human, am I safe?
Treat it as one opinion, not a guarantee. Because the two detectors are unrelated and Turnitin's own guidance warns that its scores require human interpretation, only a report in the institutional format gives you usable evidence [1][2][4].