Giant Sudoku 16x16 — The Big Board Challenge

16x16 Sudoku, also called giant Sudoku or hexadoku, is classic Sudoku on a bigger board. It is free to play online, and your game saves automatically, which helps on a puzzle this long. The sections below cover the symbols, the board and how to tackle it.

16 symbols: 1 to 9 and A to G

Sixteen digits do not exist, so the puzzle borrows letters. Here the symbols are 1 to 9 followed by A, B, C, D, E, F and G, one character per cell. They are only labels: A is not "10" in any arithmetic sense. Each row, column and box must hold all 16 symbols exactly once.

• 1
• 2
• 3
• 4
• 5
• 6
• 7
• 8
• 9
• A
• B
• C
• D
• E
• F
• G

4x4 boxes and 256 cells

The grid has 16 rows, 16 columns and sixteen 4x4 boxes, which makes 256 cells instead of 81. Every empty cell can start with up to 16 candidates, so notes fill up quickly. Givens also run higher than in 9x9. Our Easy puzzles average 151 givens and our Legendary puzzles average 94, so even the hardest boards stay over a third filled.

Same techniques, bigger board

The rules and techniques are the same as in the 9x9 game. Singles, pairs, pointing pairs and X-Wing all apply, and the six levels from Easy to Legendary use the same rating bands as the other modes. A level simply takes longer, because there is more grid to scan. Easy 16x16 puzzles are gentle in logic. If the letters feel strange, start there. Practise the first step in naked and hidden singles. Prefer paper? Print today's 16x16 sudoku from the printable Sudoku page.

Tips for a big board

• Start with the box, row or column that has the most symbols placed.
• Scan one symbol at a time across all sixteen boxes.
• Keep notes tidy and update them after every placement, as stale candidates cause most mistakes.
• Take a break when you stall. A fresh look often reveals a single you scanned past.

Where to learn

How to play 16x16 Sudoku covers the rules, a 9x9 comparison table and a step-by-step solving routine. For other grid sizes and why we host only this one, see giant and mini Sudoku.