Play 16×16 Sudoku Online
A monster grid for Sudoku veterans who want a marathon.
How to Play 16×16 Sudoku
Modes: Classic
Fill the 16×16 grid so every row, column and 4×4 box holds every symbol exactly once.
Symbols are the numbers 1–9 followed by the letters A–G.
Tap a cell and pick a symbol from the tray; use the eraser to change it.
Complete every row, column and box to finish the monster.
Rules
Each row, column and 4×4 box needs every symbol 1–9 and A–G once.
Given symbols are locked and cannot be edited.
Duplicate conflicts inside any unit are highlighted in red.
Scoring
| Solved | complete the grid |
| Time | fastest solve wins |
History & Origins of 16×16 Sudoku
The oversized branch of the family grew out of the same early-2000s Sudoku boom that produced the mini grids. Sixteen-by-sixteen boards multiply every unit fourfold, stretching a single solve well past the length of a normal puzzle and rewarding players who enjoy one long, unbroken session.
A 16×16 grid needs sixteen distinct symbols in every row, column and box, so letters carry the load once the digits run out. The layout uses the nine numbers plus seven letters, A through G, standing in for the values from ten to sixteen inside each 4×4 box.
Every board here is a marathon served at a single difficulty: about a hundred of the 256 cells start locked as givens, red marks any symbol repeated inside a unit, and the Hint button writes the next logically certain symbol. Nothing about a 16×16 rewards rushing.
Common Mistakes to Avoid
- Solving with 9×9 habits: expecting a unit to hold nine symbols leaves you blind to the extra seven. Each row, column and 4×4 box must gather all sixteen symbols once.
- Forgetting that A through G are real digits. A unit can look ’complete’ with nine numbers in place while it still needs seven letters before it is legal.
- Guessing when the grid feels stuck. With 256 cells, one wrong symbol quietly collides somewhere far away, and because every puzzle has a single solution you must backtrack rather than push forward.
- Ignoring the keyboard: you can type the letters A to G as well as the digits, and the arrow keys move your selection, which speeds up a long marathon dramatically.
Tips & Strategy
Work box by box and keep candidates in your head.
Rows and columns with one gap are free points.
Save this one for when you have time to sink in.
Frequently Asked Questions
- Is 16×16 Sudoku free to play?
- Yes — 16×16 Sudoku on ThinkyPlay is free, with no download and no sign-up.
- Which symbols does it use?
- The numbers 1 through 9 and the letters A through G — 16 unique symbols in total.
- Is there a daily 16×16?
- No — this one is a marathon puzzle served on demand.
- Why is there no difficulty selector?
- A 16×16 is inherently a Hard puzzle, so it ships as one marathon challenge. Boards start with about a hundred givens and still leave well over a hundred cells for you to place.
- Can a 16×16 be solved without guessing?
- Yes. Every puzzle comes from a pre-verified library with exactly one solution, so pure logic always suffices. If you truly stall, the Hint button reveals the next provable symbol.
- How long should I expect to spend on one grid?
- Most players settle in for 20 to 40 minutes per board, with your best solve time tracked so you can chase a personal record. It is the opposite of a quick coffee-break puzzle.