Turnitin similarity score, explained
By Sourabh Singh30 September 20265 min read
The percentage is a count of matched text, not a verdict. Here is how to read it.
The Turnitin similarity score is the percentage of your submission that matches text in Turnitin's databases: web pages, published work and other students' papers. It is not a plagiarism score. Correctly quoted and cited passages, your reference list and common phrases all count as matches, so a well-cited research paper can score higher than a short essay with one copied paragraph.
What the Turnitin colours mean
| Colour | Similarity | What it usually means |
|---|---|---|
| Blue | 0% | No matching text found |
| Green | 1 to 24% | Some matching text, often quotes, citations and common phrasing |
| Yellow | 25 to 49% | A medium amount of matching text, worth opening the report |
| Orange | 50 to 74% | A large amount of matching text |
| Red | 75 to 100% | Most of the document matches existing sources |
What is a good Turnitin similarity score?
There is no universal cut-off; it depends on the assignment and your instructor. As a rough guide, a cited essay usually lands in green, under about 15 to 20 percent. A literature review or a lab report with standard methods text can legitimately score higher. What matters is what matched: if the matches are quotes you cited and your bibliography, the score is fine even if it looks high.
Similarity score vs AI score
Turnitin reports AI writing separately from similarity. The similarity score looks for copied text; the AI writing indicator estimates how much of the text was produced by a language model. AI-generated text is usually original, so it can score 0% similarity and still be flagged as AI. Turnitin shows AI scores below 20% as an asterisk rather than a number, because false positives are more likely in that range.
How to lower your similarity score properly
- Put every direct quote in quotation marks and cite it.
- Paraphrase in your own sentence structure, not by swapping synonyms, and still cite the source.
- Ask whether your instructor excludes the bibliography and quoted material from the score; many do.
- Do not submit drafts to Turnitin through other accounts: earlier submissions can match your final paper.
Worried about the AI score rather than similarity? See which sentences read as AI.
Check for AICommon questions
For most cited essays, under about 15 to 20 percent is normal. There is no universal threshold: what matters is whether the matches are properly quoted and cited sources.
Green means 1 to 24 percent of the text matches existing sources, usually quotes, citations and common phrases. It is the most common result for a cited essay.
Not necessarily. Open the report and check what matched. If it is quotes and references, it may be fine; if whole sentences match a source without citation, fix those.
No. Turnitin reports AI writing separately. AI-generated text is usually original, so it can have low similarity and still be flagged as AI.
Weighing a switch? Turnitin alternatives, compared on real data
