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50 free Sudoku trivia questions with answers — trivia quiz, new questions added Aug 2026.
Sudoku was invented by a retired architect in Indianapolis, named in Japan by a publisher rushing to a horse race, and turned into a global craze by a Hong Kong judge who gave the puzzles away for free. Along the way it aborted an Australian jury trial, got its own live TV show and was proven to need at least 17 clues. This quiz covers the history (Number Place, Nikoli, The Times in 2004), the people (Howard Garns, Maki Kaji, Wayne Gould), the mathematics (how many solution grids exist, why the problem is NP-complete), the jargon (nonets, naked pairs, swordfish) and the variants, from Killer and Samurai to a 100×100 Sudoku-zilla. Every answer comes with a short explanation, so it works for puzzle fans, quiz nights and anyone who has ever missed their stop over a grid.
30 of 50 questions with answers and explanations. Play the quiz
Q 01In classic Sudoku, what size is the grid?
9×9
Each row, column and 3×3 box must contain every digit from 1 to 9 exactly once.
Q 02Under what name did the modern puzzle first appear in Dell Magazines in 1979?
Number Place
Japan still generally calls it Number Place, or Nanpure for short, because Sudoku is a registered trademark there.
Q 03Which retired Indiana architect most likely designed the modern Sudoku?
Howard Garns
He was 74 and freelancing as a puzzle constructor; he died in 1989, long before the craze.
Q 04How was Garns identified as the anonymous creator of the 1979 Dell puzzle?
His name was in the contributors list only in issues that ran it
New York Times crossword editor Will Shortz spotted the pattern.
Q 05Garns's colleagues at which Indianapolis firm recalled him drawing the puzzle at work?
Daggett
A draftsman remembered him covering the grid up and saying it was "a game"; it was a secret.
Q 06Which Japanese puzzle company gave the puzzle the name Sudoku?
Nikoli
The company is named after a racehorse that won the Irish 2,000 Guineas in 1980.
Q 07What does the Japanese word Sudoku literally mean?
Digit-single
It is an abbreviation of a phrase meaning "the digits must be single", taking the first kanji of each word.
Q 08Which publisher and company president is known as "the father of Sudoku"?
Maki Kaji
He reportedly coined the shortened name while scrambling to get to a horse race.
Q 09What was the puzzle magazine Kaji launched in 1980 named after?
A racehorse
The horse won the 1980 2,000 Guineas in Ireland, and Kaji loved betting on the races.
Q 10What two innovations did the puzzle's Japanese publisher introduce in 1986?
A cap of 32 givens and symmetrical clue layouts
Symmetrical means the givens sit in rotationally symmetric cells, a convention most setters still follow.
Q 11What was the profession of Wayne Gould, who spread Sudoku outside Japan?
Hong Kong judge
He saw a partly finished puzzle in a Tokyo bookshop in 1997 and spent six years writing a program to generate them.
Q 12Which was the first newspaper outside Japan to print a Sudoku, in September 2004?
The Conway Daily Sun
The New Hampshire paper beat The Times of London by two months.
Q 13What did Gould ask newspapers for in exchange for free puzzles?
A credit and a link to his site
His site sold a low-cost program, Pappocom Sudoku, that generated unlimited puzzles.
Q 21A completed Sudoku grid is a special case of which mathematical object?
A Latin square
A Latin square only needs unique rows and columns; Sudoku adds the box constraint.
Q 22Which 18th-century mathematician inspired the name of that row-and-column array?
Leonhard Euler
He used Latin letters as symbols; Korea's Choi Seok-jeong had published an order-nine example 67 years earlier.
Q 23Solving Sudoku on general n²×n² grids belongs to which complexity class?
NP-complete
Brute-force backtracking and dancing links still solve ordinary 9×9 puzzles quickly.
Q 14How did The Times of London spell the puzzle's name when it launched it in November 2004?
Su Doku
The first reader letter arrived the next day, from a man who had missed his tube stop because of it.
Q 15What did Ian Payn of Brentford complain about in the first Times letter on the puzzle?
It made him miss his tube stop
Within months the puzzle had become a front-page feature in British national papers.
Q 16Who presented Sudoku Live, the world's first live TV Sudoku show, on Sky One in 2005?
Carol Vorderman
Nine teams of nine players each solved cells on hand-held devices; the grand prize winner took over £23,000.
Q 17What was the BBC's 2005 game show combining Sudoku with general knowledge called?
SUDO-Q
It used only 4×4 and 6×6 grids and lasted four seasons.
Q 18Why was an Australian drugs trial costing over A$1 million aborted in 2008?
Jurors had been playing Sudoku
Four or five of the twelve jurors had been filling in grids instead of listening to the evidence.
Q 19What is the fewest clues a proper Sudoku can have?
17
A 2014 exhaustive computer search by McGuire, Tugemann and Civario proved no 16-clue puzzle exists.
Q 20Roughly how many completed 9×9 Sudoku solution grids exist?
About 6.67 × 10^21
Once rotations, reflections and relabellings are discounted, only 5,472,730,538 are essentially different.
Q 24A Sudoku can be expressed as what kind of problem on a network of nodes and edges?
Graph colouring
The aim is to complete a 9-colouring of a particular graph from a partial one.
Q 25Which Paris daily printed a partly filled 9×9 magic square with 3×3 subsquares in 1892?
Le Siècle
It needed arithmetic rather than logic, so it was not quite a Sudoku.
Q 26What did the newspaper La France call its near-Sudoku puzzle of 1895?
Carré magique diabolique
These weekly puzzles ran in French papers for about a decade and vanished around World War I.
Q 27What name does the Japanese term Gattai 5 describe?
Five overlapping grids in a quincunx
English-language papers such as The Times call the same layout Samurai Sudoku.
Q 28Which two puzzles does the Killer variant combine?
Sudoku and Kakuro
Cages outlined with dashes show a sum, and numbers cannot repeat within a cage.
Q 29In Killer Sudoku, what is the technique called that uses the total of any row, column or box?
The Rule of 45
A cell deduced inside the house is an "innie"; one outside is an "outie".
Q 30What is the Japanese name for Killer Sudoku, a Nipponised form of "sum num place"?
Samunamupure
The Times introduced the variant to English speakers in 2005 and briefly confused everyone over whether cages could repeat digits.