Make auto calculate for attribute

i have in 3 Attribute in item ( L , W , Area )
i need to add by manually L and W
but i need to make Area auto calculate

how i can do that

From a data standpoint, you should really be treating “Area” as an attribute, since it’s directly computed from the other two attributes. Can you say a bit more about your use case?

here i need to add length and width by meter
but in area i need to make the system calculation by auto

I understand that part. There are many ways to do what you want, and the best way depends on how length, width, and area each get used in your work flow.

The way you’ve set it up right now is probably incorrect. Area should not be a parameter. Length and width are parameters, but area is not.

If you make a Custom Field called “Area” in the Item doctype, you can use a Server Script to calculate it on_save.

how i can make that ?

how i can make this part

If you make a Custom Field called “Area” in the Item doctype, you can use a Server Script to calculate it on_save.

hello any help here

can help me for that

Might I suggest you start by examining the manual? Here’s the relevant section for what you’re trying to do:
https://docs.erpnext.com/docs/user/manual/en/customize-erpnext