Sudoku

Play Classic Sudoku

Choose a level and click on the image below to play.

Level
1
2

Sudoku 9 x 9

Play Sudoku Junior

Choose a level and click on one of the images below to play.

Level
1
2

Sudoku 4 x 4
Sudoku 6 x 6

Other Sudoku Puzzles

Choose a level and click on one of the images below to play.

Level
1
2

Sudoku 8 x 8
Sudoku 12 x 12
Sudoku 16 x 16

Rules of the game

Consider the case of a 9x9 Sudoku puzzle. In each cell, you must use the numbers 1 through 9.

In each row, a number can only be used once, so all the numbers from 1 to 9 are used.

The situation in the following image is incorrect because cells A/4 and A/7 both contain the same number 1.

Double line error

Similarly, in each column, a number can only be used once, so all the numbers from 1 to 9 are used.

And in each 3x3 block, a number can only be used once, so all the numbers from 1 to 9 are used.

Game Techniques

All the Sudoku puzzles on this page can be solved using two techniques.

The "Unique Possible Number" Technique

This occurs when only one number is possible in a cell, meaning that the other eight numbers are excluded. The reason is that these numbers are already present in the same row, column, or block as that cell.

For example :

Unique Possible Digit Technique

In cell E/7, only the digit 7 is possible because :

  • The digit 1 is located in cell E/9, on the same row as cell E/7 and also in the same block.
  • The digit 2 is located in cell E/1, on the same row as cell E/7.
  • The digit 3 is located in cell G/7, in the same column as cell E/7.
  • The digit 4 is located in cell D/8, in the same block as cell E/7.
  • The digit 5 is located in cell A/7, in the same column as cell E/7.
  • The digit 6 is located in cell F/7, in the same column as cell E/7 and also in the same block.
  • The digit 8 is located in cell H/7, in the same column as cell E/7.
  • The digit 9 is located in cell E/6, on the same row as cell E/7.

Only the digit 7 is absent from the same row, column, and block. Therefore, we can confidently place 7 in this cell.

"Single Possible Cell for a Digit" Technique

This applies when a digit is only possible in a single cell within a row, column, or block.

For example :

Unique Possible Digit Technique

In row A, one cell must contain the number 2. This number is only possible in cell A/7 :

  • We cannot place the number 2 in cell A/2 because this number is located in cell B/3 in the same block as cell A/2.
  • We cannot place the number 2 in cell A/3 because this number is located in cell B/3 in the same column and block as cell A/3.
  • We cannot place the number 2 in cell A/4 because this number is located in cell G/4 in the same column as cell A/4.
  • We cannot place the number 2 in cell A/8 because this number is located in cell H/8 in the same column as cell A/8.

Only cell A/7 remains for the number 2. We can therefore confidently place 2 in this cell.

Note: There are more advanced Sudoku techniques. But you won't need them for the grids given on this page.