Correct way to calculate capital gains on shares

When one buys or sells shares from the NSE/BSE and pays STT these are the additional expenses one incurrs :

Brokerage                        
GST                            
Securities Transaction Tax (STT)
Stamp Duty                        
SEBI Turnover Tax                
GST on  SEBI Turnover Tax.

What is the correct way to calculate short or long term capital gains on shares?

For example, can GST or STT be considered a "expense"?