Why GMs like to walk around while their oppoent is thinking?

I am just wondering that is there any particular reason that GMs start to walk around to see other games while their opponent is thinking? Because I think they should spend time to calculate the moves and think about variations.

Maybe just to freshen up their minds. If the time control is long they can afford a little walk..

First of all, strong GMs are more than capable of analyzing and thinking about the position while walking around. They have no difficulty visualizing the position.

Second, walking around stretches the legs and uncramps the body. It also promotes circulation, which aids in thinking.

by the way what is time format in classical chess?

Not just GMs, lots of players do that during long tournament games.  You gotta stretch a little, clear your mind and refresh the circulation.  I also like looking at the board from my opponent's point of view.

im not anywhere near a good chess player but the main gist is to keep blood circulating and take your mind off the game and just breathe. you can come back into the game feeling fresh.

thats boring bruh chess players r human beings too

yup

yea stretching and stuff too

Okay, I see. Thanks to you guys.

np

Every players from every level do this.

Some always stay on their chair, bad idea in my opinion.

Personnally, I do this too much and sometimes i regret but really, its difficult to stay focus all during the game.

Moreover, its a pity when u think about a move for some minutes when opponent plays something else...

lol 

I get up and walk around during OTB events sometimes - few reasons including but not limited to:

1) Long time control can afford it as said by @Uninterrupted_Chess 

2) Can still visualize while walking around and stretching as said by @Laskersnephew

3) Get another perspective like @Knights_of_Doom said, but not always from the opponent perspective. Sometimes I do that as well, but also sometimes just walking away and coming back can give a new perspective in how you view the position just as much as your literal field of view

4) I like to walk around and see how the other games are going - friends games, games from higher rated players and even games from players in same class section who I might be playing in later rounds, so I get a glance into their opening choice/play-style.

5) Conversation. Naturally, it can't be kibizing about the chess games (getting outside help/insight), but it is common for some people to quietly walk out of the playing hall together and then catch up with some small talk or something completely different from chess. Aside from the social element, it also helps mentally refresh sometimes to temporarily do nothing chess-related to refresh for when you do go back to your game.

6) Psychology. This one has many forms to it. Possibly getting up when your own clock is ticking just to slow down your anxious opponent, getting up when you are completely winning (usually positionally) just so the opponent must suffer longer in a losing position, or even getting up as a way to throw them off if they think you are not taking them seriously. The psychology can be applied in many situations, but top chess players can be really sadistic sometimes. Now imagine this compiled with cold war tensions like Fischer had against the Soviet Union. Chess really can be mental war.

7) Snacks, water, or even a bathroom break; sometimes the getting up and walking around is just something simple like this too

I could probably think of more reasons I might walk around a playing hall (or other players), but this seems like a good enough list for now.

Varies from organization or tournament. Classical time control is more of a range of possible times just like other time controls. Just like how chess.com 15/10 min games are rapid, but so are chess.com 30 min games. Usually a "classical game" is at least G90, d30 (Game in 90 min [per side] and 30 sec delay). This time control has been becoming more popular with OTB events (at least in the USCF events I may play) but this is on the "faster time control" side of classical chess. However, the "standard" of "classical chess" is probably FIDE 90 min. for first 40 moves followed by 30 min. for the rest of the game with 30 sec increment starting from move 1.

Carlsen sometimes leaves the board when he's already decided what move he's going to play next.

He gets bored waiting for his opponent, so he walks around to see the other games.

lol good use of time 

I didn't know chess.com had a whole chat like this out there.