# Why is there a default boost of 2.2?

**URL:** <https://discuss.elastic.co/t/why-is-there-a-default-boost-of-2-2/183174>\
**Category:** Elasticsearch\
**Created:** [May 28, 2019, 7:21pm UTC](https://discuss.elastic.co/t/why-is-there-a-default-boost-of-2-2/183174 "2019-05-28T19:21:29Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![slumx](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/slumx/32/47009_2.png) [@slumx](https://discuss.elastic.co/u/slumx)\
**Post date:** [May 28, 2019, 7:21pm UTC](https://discuss.elastic.co/t/why-is-there-a-default-boost-of-2-2/183174/1 "2019-05-28T19:21:29Z")

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In Elasticsearch 7.1 when no boost is added (index or query) the explanation still says there is a boost  
of 2.2.

**Steps to reproduce** :  
follow the steps described here  
[https://www.elastic.co/guide/en/elasticsearch/reference/current/getting-started-create-index.html](https://www.elastic.co/guide/en/elasticsearch/reference/current/getting-started-create-index.html)  
and here:  
[https://www.elastic.co/guide/en/elasticsearch/reference/current/getting-started-query-document.html](https://www.elastic.co/guide/en/elasticsearch/reference/current/getting-started-query-document.html)  
and do a query with explain

```auto
GET /customer/_search?pretty=true&q=doe&explain=true

```

Is this 2.2 some kind of base boost or where does i come from?

The 2.2 also appear in the documentation for explain:  
[https://www.elastic.co/guide/en/elasticsearch/reference/current/search-explain.html](https://www.elastic.co/guide/en/elasticsearch/reference/current/search-explain.html)

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<div class="post-metadata">

**Author:** ![slumx](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/slumx/32/47009_2.png) [@slumx](https://discuss.elastic.co/u/slumx)\
**Post date:** [May 29, 2019, 9:27am UTC](https://discuss.elastic.co/t/why-is-there-a-default-boost-of-2-2/183174/2 "2019-05-29T09:27:57Z")

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Figured it out, i think?. It seems that lucene removed (k1 + 1) from the bm25 similarity, so this os added as a boost instead in ES.  
see [https://issues.apache.org/jira/browse/LUCENE-8563](https://issues.apache.org/jira/browse/LUCENE-8563)

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<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [June 26, 2019, 9:28am UTC](https://discuss.elastic.co/t/why-is-there-a-default-boost-of-2-2/183174/3 "2019-06-26T09:28:05Z")

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