# Update with calculation
**URL:** https://discuss.elastic.co/t/update-with-calculation/156305
**Category:** Elasticsearch
**Created:** [November 12, 2018, 2:45pm UTC](https://discuss.elastic.co/t/update-with-calculation/156305 "2018-11-12T14:45:26Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@boeledi01](https://discuss.elastic.co/u/boeledi01)
#### Post date: [November 12, 2018, 2:45pm UTC](https://discuss.elastic.co/t/update-with-calculation/156305/1 "2018-11-12T14:45:26Z")
Hi,
We have just discovered a bug in our system which made a wrong calculation.
Fortunately for us, all documents contain enough data to reprocess the calculation.
My question
How can I run an "update" so that it recomputes a field, based on the content of other fields ?
Example:
{
"amount": 5,
"unit\_price": 25.2,
"total\_price": 30.2 (wrong value, based on erroneous calculations)
}
I would like to replace the "total\_price" by the result of "amount" \* "unit\_price" in all documents (~500000000)
Many thanks for your help
---
### Author:  [@dadoonet](https://discuss.elastic.co/u/dadoonet)
#### Post date: [November 12, 2018, 3:51pm UTC](https://discuss.elastic.co/t/update-with-calculation/156305/2 "2018-11-12T15:51:11Z")
Have a look at [https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-update-by-query.html](https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-update-by-query.html)
You can execute a script as explained in this doc.
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [December 10, 2018, 3:51pm UTC](https://discuss.elastic.co/t/update-with-calculation/156305/3 "2018-12-10T15:51:18Z")
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