What Are The 12 Rules Of Sudoku - SudokuPuzzles.net

Sudoku is a logic-based number puzzle that follows specific rules to ensure a unique solution. Understanding these 12 fundamental rules is essential for both solving puzzles and creating valid Sudoku grids.

The 12 Core Rules of Sudoku

Basic Grid Rules (3 rules)

1. Row Rule: Each row must contain all numbers 1-9 exactly once
2. Column Rule: Each column must contain all numbers 1-9 exactly once
3. Box Rule: Each 3x3 box must contain all numbers 1-9 exactly once

Solving Rules (3 rules)

4. Single Candidate: If a cell has only one possible number, it must be that number
5. Single Position: If a number can only go in one cell within a row, column, or box, place it there
6. Elimination: Use the three basic rules to eliminate impossible candidates from cells

Advanced Solving Rules (3 rules)

7. Pairs and Triples: When two or three cells contain the same candidates, eliminate those candidates from other cells in the same unit
8. Hidden Singles: Look for numbers that can only appear in one cell within a row, column, or box
9. Naked Singles: Fill cells that have only one remaining candidate

Pattern Recognition Rules (3 rules)

10. X-Wing: When a digit appears in exactly two cells in two rows and those cells are in the same columns, eliminate that digit from other cells in those columns
11. Swordfish: An extension of X-Wing involving three rows and three columns
12. XY-Wing: A pattern where three cells form a chain that allows elimination of a candidate

Why These Rules Matter

These 12 rules form the complete foundation of Sudoku solving. The first three are the basic constraints that define what makes a valid Sudoku puzzle. Rules 4-6 are the fundamental solving techniques every player should master. Rules 7-9 introduce intermediate strategies, while rules 10-12 are advanced techniques for difficult puzzles.

Applying the Rules

Start with the basic rules (1-3) to understand the puzzle structure. Then apply solving rules (4-6) systematically. As puzzles become more challenging, incorporate advanced rules (7-9) and pattern recognition (10-12). Remember, the goal is to use these rules to eliminate possibilities until only one number remains for each cell.