0%
AI Score After Humanizer
95%
Typical Unfixed AI Score
2
Separate Detection Systems
$1.45
Starting Price / Week
Two Scores. Two Problems. Two Different Fixes.
When Turnitin returns your submission results, you may see two completely separate scores — a Turnitin similarity score and a Turnitin AI score. Most students assume these are related. They are not. The turnitin similarity score vs AI score distinction is the most important thing to understand before you try to fix either one: fixing one does nothing to the other.
A student who rewrites and paraphrases to fix their similarity score is often shocked to find their AI score has not moved at all. A student who humanizes their AI-written text to fix their AI score may still have a high similarity score if they copied text from another source. These are two parallel investigations running simultaneously from the same Originality Report — and they require completely parallel fixes.
Similarity Score
Compares your text against Turnitin's database. Detects copied or insufficiently paraphrased text. Fix: rewrite and cite sources.
AI Score
Analyzes statistical language patterns to detect AI authorship — ChatGPT, Claude, Gemini. Fix: humanize with StudySolutions.
To understand how Turnitin's AI detection actually works under the hood — the language models it uses, its flagging logic, and its known limitations — see our full breakdown of how Turnitin AI detection works in 2026. For this article, we focus on the practical distinction between the two scores and exactly how to fix each one.
What Is the Turnitin Similarity Score?
The Turnitin similarity score — displayed in the Originality Report — is a percentage representing how much of your submitted text matches text in Turnitin's databases. Turnitin compares your submission against billions of student papers, academic publications, books, web pages, and previously submitted documents. Any matching text is highlighted and attributed to a source.
What the turnitin similarity percentage measures is text overlap — not plagiarism in a judicial sense, but matching text your institution may investigate. A 0% similarity score means none of your text matched any source in the database. It does not mean you did not use AI.
Turnitin Color Coding: What Each Range Means
Turnitin color-codes the turnitin originality report to give an immediate visual signal. These are the institutional defaults — your university may apply different thresholds:
The turnitin similarity threshold for academic action varies by institution. Some investigate above 20%, others only above 50%. Check your institution's academic integrity policy. The safest target is always below 20% — ideally below 10%.
What the Similarity Score Does NOT Detect
This is the critical point most students miss: the similarity score does not detect AI authorship. An essay written entirely by ChatGPT and submitted for the first time will score 0% similarity — because no matching text exists in the database yet. You can have a perfect 0% similarity score and a 95% AI score simultaneously. The Turnitin Originality Report only answers "Has this text appeared before?" — not "Was this written by a human?"
What Is the Turnitin AI Score?
The Turnitin AI score — displayed in the AI Writing Detection Report — is a percentage estimate of how much of your document was likely generated by an AI language model. Unlike the similarity score, it does not compare your text against any database. Instead, it analyzes the statistical patterns of your writing directly — specifically two measurable properties: perplexity and burstiness.
Perplexity — How Predictable Is Each Word?
AI language models always choose the highest-probability next word — producing highly predictable text (low perplexity). Human writing is more unpredictable and varied. The AI detector measures how predictable your word choices are compared to what a language model would generate.
Burstiness — How Varied Are Your Sentences?
Humans naturally mix long complex sentences with short punchy ones — high burstiness. AI produces unnaturally uniform sentence rhythms. Low burstiness combined with low perplexity is the core AI writing signature that Turnitin's classifier scores.
The turnitin ai detection percentage represents how much of your document exhibits these AI-pattern properties. A 95% AI score means 95% of your text reads with AI-characteristic statistical patterns. Most institutions investigate submissions above 20% AI-detected text — though the threshold varies. For a detailed accuracy analysis including a 1,000-essay controlled test, see our Turnitin AI detection accuracy analysis.
One important note: turnitin AI writing detection has an 8% false positive rate on genuinely human-written essays. If you wrote every word yourself but still received a high AI score, see our guide on AI detection false positives. The fix is identical either way — StudySolutions Humanizer drops the AI score to 0% regardless of whether the text was human-written or AI-generated.
Similarity Score vs AI Score: Head-to-Head Comparison
Here is the complete side-by-side breakdown of what the turnitin similarity score vs AI score actually measures, how each works, and — most importantly — how to fix each one:
The Core Asymmetry
Similarity Score — Historical Lookup
Checks if your text has appeared before. A first-time AI essay returns 0%. Originality is the signal — not authenticity.
AI Score — Statistical Analysis
Analyzes the statistical properties of the text itself — perplexity and burstiness. Has nothing to do with the database. A never-submitted AI essay still scores 95%+.
This asymmetry is why turnitin plagiarism vs AI detection is such a source of confusion. The plagiarism check looks backward in time — has this been seen before? The AI check looks at the text directly — does this read like a language model? They ask completely different questions, run completely different algorithms, and require completely different fixes.
Can Turnitin Detect ChatGPT?
Yes — but specifically through the AI score, not the similarity score. A fresh ChatGPT essay that has never been submitted before will score 0% similarity (it's original text) but will often score 90%+ on AI detection. The similarity check cannot detect ChatGPT-written text on its own. For a deeper breakdown, see our full guide on whether Turnitin can detect ChatGPT.
The 4 Possible Score Combinations — Which One Is Yours?
Since similarity score and AI score are completely independent, there are four possible outcomes when Turnitin runs on your submission. Each combination describes a different student situation — and each requires a different fix:
Combination 1: Low Similarity / Low AI → SAFE
No action needed. Your essay is original and reads as human-written. Submit with confidence.
Combination 2: High Similarity / Low AI → PLAGIARISM PROBLEM
Your text matches database sources but reads as human-written. Fix: identify flagged passages in the Originality Report, rewrite in your own voice, and add proper citations for quoted material.
Combination 3: Low Similarity / High AI → AI DETECTION PROBLEM
Your text is original (never seen before) but reads as AI-generated. Fix: run through StudySolutions Humanizer to reach 0% AI score. Your similarity score remains unaffected.
Combination 4: High Similarity / High AI → BOTH PROBLEMS
The worst case. You need both fixes: rewrite and cite flagged sources to address similarity, then humanize the AI-generated sections to address the AI score. Each fix addresses a different problem independently.
How to Lower Your Turnitin Similarity Score
If your similarity score is above your institution's threshold, here is the systematic fix. The process works by reviewing the Originality Report, identifying which passages are flagged, and addressing each one:
Step 1: Read the Originality Report
Open your Turnitin Originality Report and click through the highlighted passages. Each highlight links to the matched source. Understand what is being flagged: Is it a direct quote you forgot to cite? A paraphrase too close to the original? Not all matches are problematic — properly cited quotes and bibliography entries are expected to match.
Step 2: Rewrite Flagged Passages in Your Own Voice
For each flagged passage that represents genuine over-reliance on a source, rewrite it completely in your own words. Do not use a paraphrasing tool — Turnitin is sophisticated enough to detect synonym-swapping. True paraphrasing means understanding the source material and expressing the same idea with your own sentence structure, vocabulary, and framing.
Step 3: Add Proper Citations
For any source material you are referencing, add proper in-text citations per your citation style (APA, MLA, Chicago). Properly attributed quotations typically do not count toward your similarity threshold when your instructor has configured Turnitin to exclude quoted text. When in doubt: over-cite, not under-cite.
How to lower similarity without raising your AI score
When rewriting to fix similarity, make sure you are genuinely rewriting in your own voice — not running text through an AI tool to paraphrase it. That would reduce your similarity score while introducing AI-patterned text, raising your AI score. The goal is original human writing with proper citations.
How to Lower Your Turnitin AI Score
Fixing the Turnitin AI score requires a fundamentally different approach from fixing similarity. You are not addressing what was copied — you are addressing the measurable statistical properties (perplexity and burstiness) that Turnitin's classifier flags as AI-generated. The only reliable way to do this is with a dedicated AI humanizer.
What Does NOT Work
Reduces AI score from 98% to ~72% — still flagged. Only changes words, not statistical patterns.
Improves readability but leaves the underlying perplexity and burstiness signature intact.
Produces different AI text with the same statistical profile. Score stays high.
What Actually Works: StudySolutions Humanizer
StudySolutions Humanizer specifically targets the perplexity and burstiness patterns that Turnitin's AI classifier measures. It rewrites your text at the statistical level — not just replacing words, but altering sentence structure, rhythm, and vocabulary distribution to match natural human writing patterns. The result: 0% Turnitin AI score, guaranteed. And critically, it does not raise your similarity score — the humanized text remains original.
In a controlled test of 1,000 essays: raw AI-generated essays were flagged 96% of the time. Paraphrased AI text was still flagged 72% of the time. StudySolutions Humanizer-processed text returned 0% AI detection in every case. For a full comparison, see our best AI humanizer 2026 roundup.
To guarantee you have both scores under control before submitting, use StudySolutions Humanizer to bring AI score to 0%, then verify both scores with a real Turnitin AI report. That is the complete fix — humanize, verify, submit.
Check Both Scores Before Your Professor Does
The most important step in the entire workflow is one most students skip: run a Turnitin check yourself before submitting to your professor. When your professor runs Turnitin on your submission, the results are already locked in the system. You have no time to fix anything. If you check first, you have all the time you need.
StudySolutions: The Only Tool That Checks and Fixes Both Scores
StudySolutions gives you access to the same institutional Turnitin your professor uses — not a third-party imitator — plus the Humanizer to fix your AI score. Humanize your essay, run the Turnitin check, see both scores on the PDF report, and submit with confidence.
The Study Pass at $4.50/week bundles Humanizer + Turnitin verification — the complete stack to get both scores to 0% and prove it before you submit. For just the AI check: Turnitin Pass starting at $1.45/week. View all options on the billing page.
The workflow is: (1) Humanize your essay with StudySolutions Humanizer. (2) Submit to the StudySolutions Turnitin Check. (3) Read both Similarity and AI Score on the PDF report. (4) If similarity is high, fix flagged passages. If AI score is above 0%, humanize again. (5) When both scores are clean, submit to your professor. For the complete bypass strategy, see our guaranteed Turnitin bypass guide.
Frequently Asked Questions
Get Both Turnitin Scores to 0% — Before Your Professor Does
The Turnitin similarity score and AI score measure completely different things — and now you know exactly how to fix both. StudySolutions Humanizer brings your AI score to 0% guaranteed. The Turnitin Check shows you exactly what your professor will see — both scores — before the submission deadline. 100% undetectable, every time. Trusted by thousands of students at 500+ universities. Starting at $1.45/week.