Play 16x16 Sudoku Online
The 16x16 sudoku is the long-distance event of number puzzles: 256 squares, the numbers 1 to 16 and blocks of 4x4. The rules are the same as in classic sudoku — but the scale turns it into a different experience. At Sudoku Sagax there are 800 levels, ad-free and with no sign-up required.
What is a 16x16 sudoku?
A 16x16 sudoku follows exactly the same rules as the classic 9x9, on a board four times the size. Instead of nine digits there are sixteen numbers — here simply 1 to 16, rather than the mix of digits and letters used elsewhere, because numbers stay unambiguous to read.
The blocks are square: four rows tall, four columns wide. Sixteen blocks make up the 256 squares.
The difference is not the difficulty of individual deductions but their sheer number. A 16x16 is less forgiving of inattention, because a mistake only surfaces much later — in return it offers a solving session you can genuinely sink into.
The rules, explained simply
The same three as always, just larger:
- Rows. Each of the sixteen rows contains every number from 1 to 16 exactly once.
- Columns. The same for each of the sixteen columns.
- Blocks. Each of the sixteen 4x4 blocks contains every number exactly once as well.
Every puzzle has exactly one solution. There is no guessing here either — it simply takes longer to see everything.
Strategy for the big grid
What you can hold in your head on a 9x9 needs method here:
- Be systematic, not restless. Finish an area before moving on. Jumping around a 16x16 costs you the overview and makes you check the same places twice.
- Notes are mandatory. Nobody remembers sixteen candidates per square. Use the notes feature consistently — on a 16x16 it is a tool, not a comfort.
- Work number by number. Pick one number and look for its possible places across the whole board. That method scales with board size far better than working square by square.
- Exploit the block boundaries. Within a 4x4 block, one placed number constrains four rows and four columns at once. That interplay is stronger than on a 9x9 and the richest source of deductions.
16x16 at Sudoku Sagax
You will find 16x16 sudoku from the home screen under "All game types". There are 800 levels of its own, a separate leaderboard and its own trophy. Every level you solve counts towards your daily streak and the shared points pool.
Because a 16x16 takes considerably longer than a normal sudoku, a solved level carries correspondingly more weight in the shared scoring — it is the most heavily weighted puzzle type.
The keypad shows all sixteen keys and is fully usable on a phone; the numbers on the board scale with the board width so that two-digit values stay legible. Notes, error highlighting, hints and undo work as they do in classic sudoku.
Frequently asked questions
What is a 16x16 sudoku?
A 16x16 sudoku is a sudoku on a grid of 256 squares. Instead of nine digits it uses sixteen numbers — at Sudoku Sagax the numbers 1 to 16. The blocks are 4x4 squares, and the row, column and block rules are unchanged.
Why numbers instead of letters?
Many 16x16 sudokus use 0 to 9 plus A to F. We use the numbers 1 to 16 throughout, because they read without translation and cannot be confused with letters when you are making notes.
How long does a 16x16 sudoku take?
Considerably longer than a 9x9 — anywhere from half an hour to well over one, depending on the level and your practice. That is exactly why it carries the most weight in the shared scoring.
Is a 16x16 sudoku harder?
The individual deductions are no harder, there are simply a great many more of them. The demanding part is the bookkeeping: with sixteen candidates per square you lose track quickly without consistent notes.