Dipankar G. answered 01/31/20
International Chess Coach with 17+ years of experience
This really depends on the amount of "contact" between the White and Black pieces in the concerned position.
For example,in the starting position of the game, there is zero contact, i.e. no pieces or pawns are being attacked by either side. Hence, there is not much to calculate. You would make moves based on first principles of the opening. For example, control the center, develop your pieces etc. But after just a few moves of the opening (For example 1.e4 e5 2.Nf3 ), there is already contact between the pieces and you would have to start calculating, as to whether to defend the e5 pawn ( with 2...Nc6 or 2...d6) or ignore the attack on the e5 pawn and start a counter-attack on the e4 pawn (2...Nf6)
In general, the more contact there is between pieces, the more you need to calculate. Another case is when each side has a specific goal that they are playing for. For example, a king and pawn endgame where each side has a clear goal of promoting their pawn, you would need to calculate to determine who wins that race.
Hope this helps. Keep playing and keep calculating!