Direct answer
Grammarly does include an AI detector: its AI Detection feature estimates how much of a text was generated by AI and returns a percentage plus sentence-level highlights [1]. That verdict is not the same signal your university uses. Institutions run submissions through Turnitin, whose AI writing indicator is built on a different model, a different threshold, and a different reporting format [2]. Students who treat a Grammarly result as a preview of their Turnitin score are comparing two instruments that were never calibrated against each other [3].
Does Grammarly Have an AI Detector, and How Does It Work?
Grammarly's AI detection capability is bundled into its integrity tooling rather than sold as a standalone checker, and it is aimed primarily at institutions and professional teams reviewing large volumes of text [1]. When you run a document through it, the tool returns an overall percentage estimate of AI-generated content together with a breakdown that marks individual sentences the model considers likely machine-written [1]. That sentence-level view is genuinely useful for revision, because it tells you where the signal is concentrated instead of only giving you a number.
The mechanism behind it follows the standard pattern for commercial detectors: the text is compared against statistical properties that tend to differ between human and machine writing — perplexity, burstiness, and the regularity of word choice — and the model outputs a probability rather than a certainty [1]. Grammarly presents that probability as a percentage, which creates an intuitive but misleading impression of precision. A "40% AI" label does not mean four out of ten sentences are machine-written; it means the classifier's confidence crossed a particular band on that document [1].
It is also worth being precise about scope. Grammarly's detector evaluates text you paste or upload to it, and its output is a private advisory for whoever is using the account [1]. It does not produce a report that matches the layout, scoring bands, or flagging logic an academic integrity officer sees, and it does not interact with your institution's submission system at all [1]. Treat it as a first-pass screening tool, not a rehearsal of the real thing.
Is Grammarly's AI Detector Accurate Compared With Turnitin?
The honest answer is that the two tools answer slightly different questions, so "accuracy" comparisons between them are less meaningful than students assume [2]. Turnitin's AI writing indicator reports the proportion of qualifying prose it classifies as AI-generated, and it deliberately suppresses a precise figure when its confidence is low — which is why a Turnitin report often shows an asterisk-style low-confidence marker rather than an exact percentage [2]. Grammarly, by contrast, surfaces a percentage as its primary output [1]. Same input text, two different reporting philosophies.
Where the divergence becomes practically important is at the boundary. Turnitin's own documentation is explicit that its indicator is a signal for human judgement, not a verdict, and that false positives are possible on heavily edited, formulaic, or non-native-speaker prose [2]. Independent analyses of detector behaviour have repeatedly found that short texts, technical writing with predictable phrasing, and text that has been through grammar tools can all raise scores without any AI generation having occurred [3]. A student who polishes a handwritten essay with Grammarly's grammar suggestions can therefore see their Turnitin score move — not because Grammarly "added AI," but because the rewriting smoothed exactly the stylistic irregularity detectors key on [3].
The practical conclusion is that a low Grammarly score is weak reassurance and a high one is weak alarm. Neither number transfers to Turnitin, and neither is a substitute for seeing the report format your institution actually receives [2][3]. If the stakes are a graded submission, the only figure that matters is the one produced by the system doing the grading.
How Can Students Check Their Real Turnitin AI Score Before Submitting?
The reliable way to know your Turnitin AI score before the deadline is to obtain a report generated by Turnitin itself on your draft — the same AI detection report and similarity report your instructor would see, produced outside the institutional submission window [4]. That is precisely what turnitin0.com provides: you upload a .docx, .pdf, or .txt file (English, 300–30,000 words, under 20 MB) and receive two downloadable PDFs in a single checkout — a Turnitin AI detection report and a similarity report [4]. Checks run non-repository, so your file is not added to Turnitin's student paper database and the reports are not shared onward.
Speed matters when you are revising against a deadline. Turnitin0 reports return in under 15 minutes in 98% of cases, with most orders completing in 5–15 minutes and a guaranteed 30-minute ceiling during queue spikes. The service has delivered 100,000+ Turnitin AI and similarity reports to 20,000+ students across the US, UK, Canada, Australia, New Zealand, and Ireland, with a 4.9/5.0 satisfaction rating. Pricing is pay-per-use with no subscription: $3.80 for a single check, or $2.75 per check in a 10-check pack.
Reading the report correctly is the other half of the skill [4]. Turnitin shows a low-confidence marker instead of an exact percentage when its AI detection falls below its 20% confidence threshold, so a marked result is a weak signal rather than a clean bill of health [4]. Look at which passages are flagged, compare them against your drafting history, and revise the flagged spans in your own voice before resubmitting. Run a second check after revision to confirm the movement — that two-step loop, check then revise then re-check, is what separates students who submit calmly from students who submit and hope.
Grammarly tells you what one model thinks of your draft; it cannot tell you what your marker will see. If you want the actual report — the score bands, the flagged sentences, the similarity matches — turnitin0 puts it in your hands before the deadline rather than after it.
※ Turnitin0.com - Actual Turnitin AI Report Cover, Score, Flag And Similarity Summary
FAQ
Does Grammarly's AI detector use the same model as Turnitin?
No. They are separate commercial systems built on separate classifiers, and neither publishes a mapping between its score bands and the other's [2]. A percentage from one does not convert into a percentage from the other.
Why did my Turnitin score go up after I used Grammarly?
Grammar tools smooth out the stylistic irregularity — variable sentence length, unusual word choices — that detectors rely on to identify human writing [3]. The text is still yours; the statistical texture changed.
What does an asterisk or low-confidence marker on a Turnitin AI report mean?
Turnitin shows a low-confidence marker instead of an exact percentage when its AI detection falls below its 20% confidence threshold, meaning the signal is weak rather than conclusive [4].
Can I check my Turnitin AI score without submitting to my university?
Yes. A pre-submission check produces the same AI detection and similarity reports your instructor sees, without adding your file to Turnitin's student paper database [4].
Is one detector result ever enough to act on?
No. Detector output is a signal for human judgement, and the documented failure modes — formulaic prose, heavy editing, non-native phrasing — mean a single reading should always be verified against a second, independent report [2][3].