# Can't add math inside fields

**URL:** <https://community.homey.app/t/cant-add-math-inside-fields/132474>\
**Category:** Flows\
**Created:** [March 11, 2025, 7:36am UTC](https://community.homey.app/t/cant-add-math-inside-fields/132474 "2025-03-11T07:36:42Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![Patrick\_Spadrille](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/patrick_spadrille/32/120160_2.png) [@Patrick\_Spadrille](https://community.homey.app/u/Patrick_Spadrille)\
**Post date:** [March 11, 2025, 7:36am UTC](https://community.homey.app/t/cant-add-math-inside-fields/132474/1 "2025-03-11T07:36:42Z")

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I try to do some math inside the card to set a variable to a number. In the number field, i entered {{10+20}} but when i press ENTER, it just delete what i have put in the field. What am i doing wrong?

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**Author:** ![Rmb](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/rmb/32/79135_2.png) [@Rmb](https://community.homey.app/u/Rmb)\
**Post date:** [March 11, 2025, 8:40am UTC](https://community.homey.app/t/cant-add-math-inside-fields/132474/2 "2025-03-11T08:40:18Z")

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You are eighther using the wrong card of the wrong field. I cannot see that from here.

 ![image](https://us1.discourse-cdn.com/flex025/uploads/athom/original/3X/e/f/ef08699c1513f75f9765e0390152b5181645560d.jpeg)

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**Author:** ![Peter\_Kawa](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/peter_kawa/32/173848_2.png) [@Peter\_Kawa](https://community.homey.app/u/Peter_Kawa)\
**Post date:** [March 11, 2025, 9:49pm UTC](https://community.homey.app/t/cant-add-math-inside-fields/132474/4 "2025-03-11T21:49:07Z")

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Duplicate

> [@Available math functions](https://community.homey.app/t/available-math-functions/16622/37):
>
> I try to do some math inside the card to set a variable to a number. In the number field, i entered {{10+20}} but when i press ENTER, it just delete what i have put in the field. What am i doing wrong?

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**Author:** ![Patrick\_Spadrille](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/patrick_spadrille/32/120160_2.png) [@Patrick\_Spadrille](https://community.homey.app/u/Patrick_Spadrille)\
**Post date:** [March 12, 2025, 8:14am UTC](https://community.homey.app/t/cant-add-math-inside-fields/132474/5 "2025-03-12T08:14:50Z")

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I wasn’t using the calculate card. Does it mean i always have to use the calculate card? I can’t make calculation inside any numeric field?

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**Author:** ![Rmb](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/rmb/32/79135_2.png) [@Rmb](https://community.homey.app/u/Rmb)\
**Post date:** [March 12, 2025, 12:02pm UTC](https://community.homey.app/t/cant-add-math-inside-fields/132474/6 "2025-03-12T12:02:15Z")

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It depends on the card and the fields. I know that the app Better Logic Library offers more calculation possibilities.  
A numeric field is a numeric field, not an expression.

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**Author:** ![Peter\_Kawa](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/peter_kawa/32/173848_2.png) [@Peter\_Kawa](https://community.homey.app/u/Peter_Kawa)\
**Post date:** [March 12, 2025, 5:03pm UTC](https://community.homey.app/t/cant-add-math-inside-fields/132474/7 "2025-03-12T17:03:41Z")

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You can make calculations in many cards, but the numeric “_ **Set** _” card only takes a value or tag.