Sudoku Impasse

Occasionally when working on a Sudoku, I get to a point where I can't rule out any more possibilities and I resort to playing "what if": "what if this square is a 5?" and I take it from there. I even have a wooden Sudoku game (looks like a scrabble board) that I use to solve puzzles when I reach this point. Should it ever be necessary to use this strategy, or should all puzzles be solvable without playing "what if"?

Re : Sudoku Impasse

It depends on who has made the puzzle and who hard it is.

Most sudokus that you see in publication that are made right are supposed to be solvable just with logic.

So if you have to guess then you are missing something to solve those.

However some that are badly written will require you to guess to find the solution, and in that case you are not missing anything it is just a bad puzzle. It is hard to find out what the case is with each puzzle but there are some online solvers that will tell you the rule used in order to solve it.

Search for scanraid and you can input a sudoku and it will tell you how it solved it, this will teach you if there are just hard rules you are missing or infact if the puzzle is a bad one that requires guessing to solve it.