16x16 Sudoku (Hexadoku)

A larger 16×16 grid split into 4×4 boxes — fill every row, column and box with the sixteen symbols 0–9 and A–F. A bigger, hexadecimal twist on classic sudoku.

How 16×16 sudoku works

Each row, each column and each 4×4 box must contain the sixteen symbols 0–9 and A–F exactly once — no repeats anywhere in a row, a column or a box. Some cells start filled in as fixed clues; the rest are empty for you to complete. Tap a cell to select it, then choose a symbol from the number pad below the board — or use Hint if you get stuck, or Solve to reveal the finished grid. The rules are identical to classic 9×9 sudoku, just scaled up: the same logic techniques, like a row or box that's almost full, or a cell with only one legal symbol left, still solve the puzzle. Prefer the classic game? Try 9×9 sudoku at Easy or Hard difficulty, work out cage totals with the Killer Sudoku combinations calculator, grab a printable sudoku, or read how to play Sudoku.

Frequently asked questions

What symbols does 16x16 sudoku use?

16×16 sudoku uses the sixteen hexadecimal symbols 0–9 and A–F instead of the digits 1–9 used in classic sudoku. Each row, column and box must contain all sixteen symbols exactly once. Because there are only sixteen distinct symbols to track, the digits and letters fill the same role a bigger digit set like 1–16 would, without needing two-character numbers in each cell.

How big are the boxes in 16x16 sudoku?

Each box is 4 rows by 4 columns — a 4×4 block. The whole grid is 16×16, made up of sixteen of these 4×4 boxes arranged in a 4×4 pattern. That's the same total cell count as the 9×9 grid's nine 3×3 boxes, just rearranged into a 4-by-4 layout of boxes instead of 3-by-3.

Is 16x16 sudoku harder than 9x9?

Yes — 16×16 sudoku is harder than 9×9. The larger grid and greater number of symbols mean more cells to track and more candidates to eliminate, but the same logic applies. Every generated puzzle still has exactly one solution.

How many clues does a 16x16 sudoku puzzle start with?

Each new 16×16 puzzle starts with 150 filled clues out of 256 cells, roughly 59% of the grid. That's enough to guarantee a unique solution without giving away the whole board. Use Hint if you get stuck on the rest.