Sudoku rules
Complete guide to game rules and solving techniques. With interactive examples.
What is Sudoku
Sudoku is a popular number logic game. The rules are simple, so even beginners can manage the easier levels. All you need is a brain, focus, and a little patience.
5
3
7
6
1
9
5
9
8
6
8
6
3
4
8
3
1
7
2
6
6
2
8
4
1
9
5
8
7
9
The board
A sudoku diagram is a 9×9 grid of cells divided into 9 boxes of 3×3. Some cells are filled at the start, we call them givens. The rest is your job.
Row or column3×3 boxIntersection cell
Short rules
You use only digits from 1 to 9.
Each 3×3 box contains every digit from 1 to 9 exactly once.
Each vertical column contains every digit from 1 to 9 exactly once.
Each horizontal row contains every digit from 1 to 9 exactly once.
No digit repeats within a box, column or row.
The game ends when the entire diagram is correctly filled.
Basic rules
Each digit once per row
In each of 9 horizontal rows every digit 1–9 must appear exactly once.
Each digit once per column
In each of 9 vertical columns every digit 1–9 must appear exactly once.
Each digit once per box
In each of 9 boxes of 3×3 every digit 1–9 must appear exactly once.
Every well-formed sudoku has exactly one solution. You don't need to guess, everything can be deduced logically.
What counts as a mistake
A move is invalid if it causes:
the same digit to appear twice in one row.
the same digit to appear twice in one column.
the same digit to appear twice in one 3×3 box.
Time to practice
You learn best by playing. Every new puzzle is a chance to try the techniques you just read about. The Hint button in the game will show you which technique to apply.
Play now