Learning center Sudoku strategies
Five patterns that
unlock the grid.
Start with the simplest pattern available. Each correct placement creates new information, often turning a difficult board into a series of easy singles.
Full house
When a row, column, or box has eight numbers filled, the one missing number must go in the final square.
Naked single
If an empty square can accept only one number after checking its row, column, and box, place that number.
Hidden single
A number may fit several squares at first glance, but only one square within a row, column, or box may actually accept it.
Crosshatching
Use the same number in neighboring boxes to eliminate rows and columns, revealing where that number belongs in the remaining box.
Candidate pairs
If two squares in one unit share the same two candidates, those numbers can be removed from every other square in that unit.
What should you avoid?
Do not guess early. Do not focus on one corner for too long. And do not forget to update pencil marks after placing a number—old candidates cause avoidable mistakes.