Sudoku Rules
Sudoku is a logic puzzle with simple rules but challenging solutions. Here you'll find all the official game rules clearly explained.
The Playing Field
- ●A sudoku consists of a 9×9 grid with 81 cells
- ●The grid is divided into 9 blocks of 3×3 cells
- ●Each cell ultimately contains one number from 1 to 9
- ●The puzzle starts with some pre-filled numbers (given numbers)
The Three Main Rules
The Row Rule
Each number from 1 to 9 may only appear once in each horizontal row. There are 9 rows in the grid.
The Column Rule
Each number from 1 to 9 may only appear once in each vertical column. There are 9 columns in the grid.
The Box Rule
Each number from 1 to 9 may only appear once in each 3x3 box. There are 9 boxes in the grid.
Important Characteristics
Unique Solution
A valid sudoku puzzle always has exactly one unique solution. If multiple solutions are possible, the puzzle is not correctly designed.
No Guessing Needed
Every sudoku can be solved through logical reasoning. Guessing is never necessary if you apply the right techniques.
Given Numbers
The pre-filled numbers (clues) determine the difficulty level. Fewer clues usually means a harder puzzle.
Symmetry
Many puzzles have a symmetrical pattern of given numbers, although this is not an official requirement.
Difficulty Levels
The difficulty of a sudoku is determined by the number of given numbers and which techniques are needed to solve it:
Note: 17 is the proven minimum number of clues for a valid sudoku with a unique solution.
Frequently Asked Questions
Can I guess if I get stuck?
Technically you can, but it's not in the spirit of sudoku. Every well-designed puzzle can be solved with logic. Try other techniques first.
What if I made a mistake?
Use the undo function or clear the cell. It's important to correct mistakes before continuing, otherwise they lead to more mistakes.
Are there sudoku variants?
Yes, there are many variants such as Killer Sudoku, Diagonal Sudoku, Irregular Sudoku, and more. These add extra rules to the standard rules.