# Calculate duration

**URL:** <https://community.homey.app/t/calculate-duration/34309>\
**Category:** Questions & Help\
**Tags:** flow\
**Created:** [September 3, 2020, 11:43am UTC](https://community.homey.app/t/calculate-duration/34309 "2020-09-03T11:43:12Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![M\_Avramoski](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/m_avramoski/32/13549_2.png) [@M\_Avramoski](https://community.homey.app/u/M_Avramoski)\
**Post date:** [September 3, 2020, 11:43am UTC](https://community.homey.app/t/calculate-duration/34309/1 "2020-09-03T11:43:12Z")

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I’m trying to calculate the duration of the time my pool pump needs to run, based on the water temperature.  
The flow itself works, when trying an easier formula {{(temperatuur/2)\*3600}} for example, then it works.  
But the formula i’m trying to set is {{((Temperatuur/2)-(0,2 \*Temperatuur))\*3600}}  
However, i’m not getting any value stored in my variable.  
It’s probably a syntax error, but i can’t figure out which one.

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**Author:** ![Marcel\_Ubels](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/marcel_ubels/32/18860_2.png) [@Marcel\_Ubels](https://community.homey.app/u/Marcel_Ubels)\
**Post date:** [September 3, 2020, 12:11pm UTC](https://community.homey.app/t/calculate-duration/34309/2 "2020-09-03T12:11:34Z")

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> [@M\_Avramoski](#):
>
> {{((Temperatuur/2)-(0,2 \*Temperatuur))\*3600}}

Suppose it is **.** Instead off **,**

So {{((Temperatuur/2)-(0.2 \*Temperatuur))\*3600}} will do the trick

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<div class="post-metadata">

**Author:** ![M\_Avramoski](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/m_avramoski/32/13549_2.png) [@M\_Avramoski](https://community.homey.app/u/M_Avramoski)\
**Post date:** [September 3, 2020, 12:13pm UTC](https://community.homey.app/t/calculate-duration/34309/3 "2020-09-03T12:13:24Z")

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Thanks that worked!

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**Author:** ![MadMax](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/madmax/32/10306_2.png) [@MadMax](https://community.homey.app/u/MadMax)\
**Post date:** [September 3, 2020, 12:20pm UTC](https://community.homey.app/t/calculate-duration/34309/4 "2020-09-03T12:20:35Z")

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Could you share your flow?

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<div class="post-metadata">

**Author:** ![M\_Avramoski](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/m_avramoski/32/13549_2.png) [@M\_Avramoski](https://community.homey.app/u/M_Avramoski)\
**Post date:** [September 4, 2020, 6:33am UTC](https://community.homey.app/t/calculate-duration/34309/5 "2020-09-04T06:33:37Z")

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[https://homey.app/f/G80Qnh](https://homey.app/f/G80Qnh)