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how many moves an average player is supposed to calculate in advance?
If you can accurately calculate 3 moves in advance, that would be more than sufficient and you'd be a damn good player.
Hell, if you just avoid obvious blunders, you are already better than average.
It really depends on how forcing the line be calculate is. I played a 6-7 move combination against an old nintendo game being emulated on a modern computer, required 12-14 plys. Too deep for an 8 bit system, but forcing enough for a human to see. I remember this clearly because of how surprised I was that a machine blundered. I wish I preserved the game.
If you did that (always see forcing moves atleast 3-ply ahead) 100% of the time ( in all games with ALL moves ) , you are very likely a strong club player and better than 80% of all chess players on the planet.
Though this is easier "said" than actually done and takes remarkable levels of mental discipline to calculate forcing lines concretely at ALL TIMES ... even if they are just a measly 3 plies :)
I've yet to meet a sub-1800 OTB player who "never misses" a 3-ply shot in a slow time control game (yours truly included). Even the 1800-2000 players have lapses in concentration and miss things ... though they are statistically more cleaner/consistent than the other class players.
In his Power Chess for Kids book, I think Hertan amusingly calls application of this "3-ply forcing move calculation" ==> "Takes, takes, bang!" :)
A related point that I may not have made clearly is that trying to push your own "horizon effect" during chess study is very beneficial to your ability to calculate. You know the feeling, you can sit down and see 3 or 4 moves deep, but then things get kind of fuzzy. I would suggest working on that fuzzy area while looking at a board. I suppose it is a shame that our modern computers are not set up to help us with this training.
So when you solve a tactical problem record your thoughts as deeply as possible before what you see as deeply as possible before checking the answer, seeing one move deep is not a solution, nor is the problem solved if you only saw one line when you really needed to see three.