BM25 calculator
Enter a query and documents to see how BM25 ranks results by term matches, document length, and parameters.
BM25 calculator for BM25 algorithm and search ranking
The BM25 calculator helps debug keyword search by showing BM25 scores for a query and candidate documents. Use it to inspect how the BM25 algorithm balances term frequency, document length, and inverse document frequency. When a result ranks higher, the ranking view shows which terms matched and how the BM25 formula changed the score. This makes BM25 search easier to explain before you tune search or compare content.
BM25 calculator query
Enter a real query to see which terms drive BM25 ranking.
BM25 ranking documents
Paste candidate documents and compare how the BM25 calculator scores each document with the BM25 formula.
BM25 formula parameters
Adjust k1 and b to see how the BM25 formula changes BM25 ranking order.
How to use BM25 calculator
Use it in three steps.
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01
Enter the search query.
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02
Paste one or more candidate documents.
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03
Adjust k1 and b to see how scores and ranking change.
Formula
How BM25 scores documents.
Score
score(D,Q) = sum IDF(q) * tf(q,D) * (k1 + 1) / (tf(q,D) + k1 * (1 - b + b * |D| / avgdl))
Parameters
k1 controls term saturation. b controls length normalization.
BM25 calculator FAQ
What is BM25?
BM25 is a lexical ranking formula that scores documents by query term matches, term frequency, document length, and inverse document frequency.
How does BM25 score documents?
It compares query terms with each document, weighs repeated matches, normalizes document length, and returns a relevance score. The BM25 calculator makes those scoring changes visible.
Should I change k1 or b?
Start with defaults, then adjust k1 for term-frequency saturation and b for document-length normalization.
Is BM25 semantic search?
No. BM25 is keyword-based lexical search, not semantic vector search.
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