## Introduction to sudoku

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See also* -
Sudoku solver |
Solving sudoku

**What is sudoku?**

A sudoku consists of a grid as below...

…and you are given the instructions "

Translated from Japanese, the term litreally means "number place". It is common for sudoku to be called "number place" in the United States.

Personally, I go for Sudoku, but any of these three are acceptable.

A proper sudoku will be solveable by making logical deductions as to what numbers can and can't go in each square. When all 81 squares are filled, you have completed the puzzle. For a more detailed guide on how to go about solving sudoku, have a look at my solving sudoku page.

A proper sudoku is one which can be solved only by making logical deductions. However, there are some sudokus out there that require guesswork in order to reach a solution. Personally I think this takes away from the fun of solving sudoku. This is because it is often said that to be good at sudoku you don't need to be good at maths - all that is required is a clear head and logical thinking.

Yes - though this means that guesswork will be required to arrive at the solutions to the puzzle. In such a case, when solving the puzzle, you will reach a point at which you can make no more logical deductions, thereby forcing you to guess.

Many sudokus, such as the one above, have rotational symmetry about the central square with regards to which squares are filled and which are blank. Though this is by no means a requirement to a sudoku puzzle, it gives the puzzle a somewhat aesthetic quality.

This depends on both the puzzle's difficulty and your own experience.

My favourites sudoku sources are websudoku.com and sudokus from

*Fill the grid so that each row, column and 3 x 3 box contains the numbers 1 to 9”*.

What does sudoku actually mean?What does sudoku actually mean?

Translated from Japanese, the term litreally means "number place". It is common for sudoku to be called "number place" in the United States.

Sudoku, SuDoku or Su Doku?Sudoku, SuDoku or Su Doku?

Personally, I go for Sudoku, but any of these three are acceptable.

So how do you go about solving them?So how do you go about solving them?

A proper sudoku will be solveable by making logical deductions as to what numbers can and can't go in each square. When all 81 squares are filled, you have completed the puzzle. For a more detailed guide on how to go about solving sudoku, have a look at my solving sudoku page.

What do you mean by a "proper" sudoku?What do you mean by a "proper" sudoku?

A proper sudoku is one which can be solved only by making logical deductions. However, there are some sudokus out there that require guesswork in order to reach a solution. Personally I think this takes away from the fun of solving sudoku. This is because it is often said that to be good at sudoku you don't need to be good at maths - all that is required is a clear head and logical thinking.

Can a sudoku have more than one solution?Can a sudoku have more than one solution?

Yes - though this means that guesswork will be required to arrive at the solutions to the puzzle. In such a case, when solving the puzzle, you will reach a point at which you can make no more logical deductions, thereby forcing you to guess.

**Yes. For an example of such a sudoku, download my Sudoku solver and try puzzle number 5.**

Can a sudoku have a unique solution, but require guesswork?

Can a sudoku have a unique solution, but require guesswork?

What is it with symmetry and sudoku?What is it with symmetry and sudoku?

Many sudokus, such as the one above, have rotational symmetry about the central square with regards to which squares are filled and which are blank. Though this is by no means a requirement to a sudoku puzzle, it gives the puzzle a somewhat aesthetic quality.

How long do sudokus take to solve?How long do sudokus take to solve?

This depends on both the puzzle's difficulty and your own experience.

*The Times*newspaper grades its puzzles "easy", "medium", "difficult" and "fiendish". Someone with reasonable experience at Sudoku may be able to finish an easy puzzle in five minutes or less, whereas a fiendish puzzle could take around half an hour.

Where can I find sudoku on the Internet?Where can I find sudoku on the Internet?

My favourites sudoku sources are websudoku.com and sudokus from

*The Times*newspaper. All the sudokus obtained from these websites have unique solutions, and no guesswork is required.