How to Use the Plagiarism Calculator
Paste the first text in the left textarea and the second text in the right textarea. The calculator instantly analyzes both texts by breaking them into 3-grams (sequences of three consecutive words) and computing the Jaccard similarity coefficient. The results show the similarity percentage, the number of matching phrases, and the total unique phrases in each text.
This tool is designed for students who want to check their work against source material before submitting assignments. It helps identify passages that may need additional paraphrasing or proper citation. All processing happens in your browser, so your text is never sent to any server.
Understanding the Jaccard Similarity Coefficient
The Jaccard similarity coefficient measures the overlap between two sets. In this tool, it calculates the ratio of shared 3-grams to the total unique 3-grams across both texts. A score of 0% means no matching phrases, while 100% means the texts share identical phrasing. The 3-gram approach is effective because it catches phrase-level copying that single-word frequency analysis would miss, while remaining resilient to minor word substitutions.
Interpreting Your Results
A similarity below 15% typically indicates original writing with common phrases. Between 15% and 40% suggests moderate overlap that may warrant review, especially if the matching phrases come from a specific source rather than general academic language. Above 40% indicates significant textual similarity and likely requires substantial revision or proper attribution. Technical and scientific writing naturally uses more standardized phrasing, so higher baseline similarity is expected in those fields.
Tips for Reducing Similarity
Read the source material, then write your understanding in your own words without looking at the original. Use synonyms and restructure sentences, but ensure the meaning remains accurate. Direct quotes should be enclosed in quotation marks with proper citations. Focus on synthesizing ideas from multiple sources rather than relying heavily on any single source. After writing, use this tool to compare your text against the source and revise any passages that still show high similarity.
Frequently Asked Questions
How does the plagiarism calculator work?
The calculator normalizes both texts by converting to lowercase and removing punctuation, then generates 3-grams from each text. It uses the Jaccard similarity coefficient to calculate the percentage of matching 3-grams relative to the total unique 3-grams across both texts.
What is a 3-gram in text analysis?
A 3-gram is a sequence of three consecutive words from a text. For example, "the quick brown fox" produces the 3-grams: "the quick brown" and "quick brown fox". Comparing 3-grams catches phrase-level similarities that single-word comparison would miss.
What similarity percentage indicates plagiarism?
There is no universal threshold. Below 15% is typically acceptable, 15-40% suggests moderate overlap worth reviewing, and above 40% indicates significant similarity requiring attention. Context matters: technical writing naturally has higher overlap.
Does this tool detect paraphrasing?
This tool detects exact phrase matches using 3-gram comparison. Heavily paraphrased content with entirely different word choices may not be detected. Use this alongside other analysis methods for comprehensive checking.
Is my text stored or shared?
No. All processing happens in your browser using JavaScript. Your text is never sent to any server, stored, or shared.
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