Understanding Sudoku Grading: Difficulty Levels from 0 to 8+

Sudoku difficulty usually follows a numerical scale where 0 is easiest and 8+ is extreme. Each level reflects the techniques needed for solution.

Grade 0 (Very Easy)

• Basic scanning and single-candidate filling.
• Suitable for beginners.

Grade 1 (Easy)

• Naked singles and basic cross-checking.

Grade 2 (Moderate)

• Hidden singles and optional pencil marks.

Grade 3 (Challenging)

• Naked pairs and intersection removal.

Grade 4 (Hard)

• Hidden pairs, naked triples, and box-line reduction.

Grade 5 (Very Hard)

• X-Wing and Swordfish patterns appear.

Grade 6 (Expert)

• Advanced elimination such as XY-Wing techniques.

Grade 7 (Master)

• Coloring and forcing chains become common.

Grade 8+ (Extreme)

• Highest-level strategy such as uniqueness tests and advanced set logic.