how to calculate SQL standard edition licensing If I have 1 vm with 7

Check this link

https://www.microsoft.com/en-sa/sql-server/sql-server-2019-pricing

+1

There are two types of licensing:

Core Based Licensing, and Server + CAL Licensing.

In your case, you need core based licensing.

SQL standard cost per core and comes with 2 core pack.

+1

Check this article for clear concept on licensing.

https://metrixdata360.com/license-series/sql-server-licensing-explained/

+1

basically it is 2core = 1 license

+1