Frequently asked questions
If you have a question about your account, generating, or solving, please see our Members' FAQ.
What does “Sudoku” mean?
Sudoku or “su doku” () translates “number allotted” or “the number that is single” in Japanese. Details on the origin of the word and the correct pronunciation are available at JapaneseTranslator.co.uk.
For how long has the puzzle existed?
The recognised puzzle of Sudoku first arrived in a magazine called Nikoli in Japan in the late 1980s, having previously been published in the late 1970s by the New York puzzle magazine Math Problems and Logic Puzzles, published by Dell, under the title "Number Place". It may have originated from a game called Latin Squares or Magic Squares thought up by the Swiss mathematician, Leonhard Euler. He invented Magic Squares or “carrés magiques” in 1783. Magic Squares had fewer restrictions than Sudoku with no lines dividing the square.
What are the rules of the game?
The rules of the game simply require that the grid is completed with different numbers in every row, column and box. The existing numbers cannot be changed or moved. In a correctly formed Sudoku puzzle, there is one unique solution.
Does it require knowledge of maths?
No, Sudoku does not require any knowledge of mathematics to solve. However, Sudoku does require logic and reasoning. The use of numbers offers one method of identification – letters, colours, symbols, photos or anything else could offer identifiers for the cells.
Why is the game so addictive?
The identification of symmetrical patterns draws on the addictive aspect of the brain. Sudoku offers a challenge to the brain that encourages logical thought processes utilising the short-term memory. It is thought that this type of puzzle helps prevent the advance of Alzheimer's and offers some comfort for short-term illness through its therapeutic thought patterns.
How long does it take to complete a Sudoku puzzle?
A three-by-three Sudoku puzzle will take between 10 to 30 minutes to complete depending on your skill and expertise and the difficulty of the puzzle.
Four-by-four Sudoku puzzles will take much longer to complete. As these puzzles are much larger than three-by-three puzzles, they usually take upwards of two hours.
How many solutions are there?
For a correctly formed Sudoku puzzle, there should be only one solution. Some variants on Sudoku do have more than one solution; these should not be confused with a true Sudoku puzzle.
Earlier in the year, Sky One gained its place in the record books for the largest Sudoku in the world. Unfortunately for them, this is a mal-formed non-unique puzzle, so technically it is not a Sudoku.
What is the difference between symmetrical and non-symmetrical Sudoku?
A Sudoku has no requirement to be either symmetrical or asymmetrical. People may argue that one approach has advantages over another, but differences in solving each type of Sudoku are negligible.
However, we believe that Sudoku are better when they are asymmetrical as there is greater freedom to create challenging and varied Sudoku puzzles. Unlike crosswords, Sudoku puzzles change as you solve, rendering any symmetrical layout obsolete.
At Sudoku Solver, we generate both symmetrical and asymmetrical Sudoku and Super Sudoku. Full members have the choice of symmetry in their Sudoku in their preferences.
Where can I find new Sudoku puzzles?
As well as generating your own Sudoku and Super Sudoku puzzles here, you can find three-by-three Sudoku puzzles in these UK newspapers:
The Times and The Sunday Times
The Independent and The Independent on Sunday,
The Sun and
The Daily Telegraph.
The more difficult four-by-four
Sudoku puzzles can be found every Saturday in:
Star Magazine, USA.
Please have a look at some of our Sudoku website links for newspaper Sudoku links other online Sudoku puzzles.