# Bucket aggregation - calculate my own metric inside bucket
**URL:** https://discuss.elastic.co/t/bucket-aggregation-calculate-my-own-metric-inside-bucket/291326
**Category:** Elasticsearch
**Created:** [December 9, 2021, 12:42pm UTC](https://discuss.elastic.co/t/bucket-aggregation-calculate-my-own-metric-inside-bucket/291326 "2021-12-09T12:42:42Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@Detlic\_Detlicko](https://discuss.elastic.co/u/Detlic_Detlicko)
#### Post date: [December 9, 2021, 12:42pm UTC](https://discuss.elastic.co/t/bucket-aggregation-calculate-my-own-metric-inside-bucket/291326/1 "2021-12-09T12:42:42Z")
Hello,
i collect data from my router and store into Elasticsearch.
My data mappings are in this form : \< {"interface\_name":"keyword", "value":"double", "timestamp":"integer"}. \>
I need to measure flow for each interface like: \< flow = (v2-v1)/(t2-t1) \>.
So if i have for an example two interfaces with same name
(interface:"i1" value: 5 ts: 2) and (interface: "i1" value:10 ts:3 ) i need to get (10-5)/(3-2) as output.
I group each interface into bucket with bucket aggregation and i know how to get avg/max/min, but i don't know how to calculate with my own formula.
This is my first post on forum,
Thank you in advance!
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [January 6, 2022, 12:43pm UTC](https://discuss.elastic.co/t/bucket-aggregation-calculate-my-own-metric-inside-bucket/291326/2 "2022-01-06T12:43:26Z")
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