What is 16×16 Sudoku?

16×16 Sudoku scales the classic puzzle to a 16×16 grid divided into sixteen 4×4 boxes. Instead of digits 1–9, you use sixteen symbols: the digits 1–9 and the letters A through G. Every row, every column, and every 4×4 box must contain all sixteen symbols exactly once. The larger grid demands greater concentration and more systematic candidate tracking, making it a rewarding challenge for experienced Sudoku solvers.

How to Play 16×16 Sudoku

• Use the same rules as classic Sudoku

  Every row, column, and 4×4 box must contain the symbols 1–9 and A–G without repetition. All standard solving techniques apply.

• Track candidates systematically

  With 16 possible symbols per cell, pencil marks are essential. Enable candidate fill and auto-remove to keep track of possibilities as you progress.

• Focus on the most-filled regions

  Start with rows, columns, and boxes that already have the most symbols placed. Fewer missing symbols means fewer candidates to consider.

• Apply advanced techniques

  Hidden singles, naked pairs, pointing pairs, and X-Wing patterns all work in 16×16. The larger grid just means more cells to scan — the logic is identical.

Tips & Tricks

• Group by Number vs Letter

  Mentally separate the digit symbols (1–9) from the letter symbols (A–G). Solving one group often reveals where the other group must go within the same row or box.

• Start Dense, Work Outward

  Find the row, column, or box closest to complete and solve it first. Each resolved cell reduces the candidate pool for connected regions.

• Pencil Marks Are Non-Negotiable

  At 16×16 scale, mentally tracking candidates is impractical. Use pencil marks from the start. The auto-remove candidates feature will clean them up automatically as cells are confirmed.

• Same Techniques, Bigger Grid

  X-Wing, Swordfish, and Unique Rectangles all scale perfectly to 16×16. If you've mastered these in classic Sudoku, you already have the tools to tackle the hardest 16×16 puzzles.