A Turnitin report shows two separate numbers: a Similarity Score for text matching other sources, and an AI writing indicator estimating AI-generated content. Neither is a plagiarism verdict — the colour and percentage just flag text for a human to review.
Key Takeaways
- A Turnitin report contains two independent metrics: the Similarity Score and the AI writing indicator, per Turnitin’s similarity-score guide.
- The Similarity Score measures matching text, including quotes, references and common phrasing — not just copied work.
- A high percentage is a prompt to review which sources matched, not proof of misconduct.
- You can often exclude quotes and the bibliography, which changes the number substantially.
- The colour band summarises the similarity percentage; read the number, not just the colour.
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The single biggest source of confusion is that students see one percentage and assume it is “the plagiarism score.” A Turnitin report actually reports two different things. The Similarity Score measures how much of your text matches Turnitin’s database, and the AI writing indicator separately estimates how much reads as AI-generated. They are calculated differently and mean different things, as Turnitin explains in its student guide to the similarity score.
The Similarity Score and AI indicator are two different numbers.
How do you read the Similarity Score?
The Similarity Score is a percentage with a colour band attached — and that colour scale is explained in full in our guide to what Turnitin colours mean. What matters is what is matching, not just the number. Open the match breakdown and look at each source: a string of matches against a quote you cited correctly is very different from a paragraph lifted from a website. University guidance such as NCI’s Turnitin FAQ and Boise State’s interpretation guide and the University of the Witwatersrand’s guidance all stress reading the sources, not reacting to the headline figure.
Common sources of a high (but harmless) similarity percentage.
| What you see | What it usually means |
|---|---|
| Matches on quoted passages | Expected — can often be excluded |
| Matches on your reference list | Normal — bibliography can be excluded |
| Matches to one external site | Review closely — is it cited? |
| Matches to your own prior draft | Ask instructor to exclude previous submissions |
How do you read the AI indicator?
The AI writing indicator is a separate percentage and does not use the similarity colour scale. It estimates how much of the text reads as AI-generated, and it is far more contested than similarity matching. Our guides to how the Turnitin AI checker works and AI-detection false-positive rates by tool cover how reliable that number actually is — and why a flag is not a conviction. If only one section lit up, here’s why one part of an essay can be flagged more than another.
Does a high score mean you plagiarised?
No. Both numbers flag text for review; neither decides misconduct. A correctly quoted, fully cited essay can still show a chunky similarity percentage, and a genuine human draft can trip the AI indicator. For the full picture of how scores translate into outcomes, see what detection-report scores really mean and what to check when Turnitin flags your references page.
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Frequently asked questions
What is a Turnitin similarity report?
It is the breakdown showing which parts of your submission match other sources, expressed as a percentage with a colour band, plus a separate AI writing indicator.
Is the Turnitin percentage the plagiarism score?
No. It measures matching text, which includes quotes, references and common phrasing. It flags text to review, not proof of plagiarism.
Why is my reference list matching in Turnitin?
Bibliographies naturally match other citations of the same sources. This can usually be excluded from the score by you or your instructor.
Is the AI score the same as the similarity score?
No. They are two separate numbers. The AI indicator estimates AI-generated writing and does not use the similarity colour scale.
How do I lower my similarity score?
Quote and cite properly, paraphrase in your own words, and exclude quotes and bibliography where allowed. Remember instant resubmissions are limited to three per 24 hours.
Can I see which sources matched?
Yes. Open the match breakdown in the report to see each matching source and decide whether it is a properly cited quote or a genuine problem.
Methodology: report structure and interpretation are drawn from Turnitin’s published Guides and university library guidance (NCI, Boise State). Last updated: July 2026.
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