Sudoku Trivia
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36 free Sudoku trivia questions with answers — trivia quiz, new questions added Sep 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 36 questions with answers and explanations. Play the quiz
Q 01Which kind of reasoning does solving a Sudoku rely on?
Logic
Logic is all it takes: the digits are only labels, so any nine different symbols would make the same puzzle.
Q 02Under what name did Sudoku first appear in Dell Magazines in 1979?
Number Place
Number Place was the name at Dell in New York, so the puzzle famous under a Japanese name actually began in an American magazine.
Q 03Which retired Indiana architect most likely designed the modern Sudoku?
Howard Garns
Howard Garns died in 1989, years before his puzzle became a worldwide craze under a Japanese name.
Q 04How was the anonymous creator of Dell's 1979 grid puzzle identified?
His name only appeared in issues with it
His name only appeared in issues with it, a pattern a New York Times crossword editor spotted by checking back issues.
Q 05Which YouTube channel, run by two British puzzle experts, became a lockdown hit by solving Sudokus live on camera?
Cracking the Cryptic
Cracking the Cryptic took off after co-host Simon Anthony quit his investment banking job to solve puzzles on YouTube.
Q 06Which British newspaper parodied the 2005 Sudoku craze by printing a grid on every page of a supplement?
The Guardian
The Guardian put a Sudoku on every page of its G2 section, cover included, while joking that its puzzles were hand-crafted by masters.
Q 07What does the Japanese word Sudoku literally mean?
Digit-single
Digit-single is the literal sense, because the puzzle's longer original name, 'the numbers must be single', was cut down to Sudoku.
Q 08Which publisher and company president is known as "the father of Sudoku"?
Maki Kaji
Maki Kaji dropped out of university before founding the puzzle magazine that gave Sudoku its name.
Q 09Which Stanford computer scientist gave 'dancing links', a classic technique for solving Sudoku by computer, its name?
Donald Knuth
Donald Knuth named the technique, but he credited the underlying trick to a 1979 paper by Hitotumatu and Noshita.
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
Hong Kong judge Wayne Gould found a Sudoku book in a Tokyo bookshop in 1997 and spent six years writing a program to generate puzzles.
Q 12Which was the first newspaper outside Japan to print a Sudoku, in September 2004?
The Conway Daily Sun
The Conway Daily Sun, a small New Hampshire free paper, beat The Times of London to Gould's puzzles by two months.
Q 13What did Gould ask newspapers for in exchange for free puzzles?
A credit and a link to his site
Q 21A 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 22Which country's newspapers printed Sudoku-like number grids in the 1890s, decades before Dell's version?
France
France: an 1895 puzzle in the daily La France came closest to modern Sudoku, yet it never marked the 3×3 boxes.
Q 23What 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.
A credit and a link to his site were enough, because Gould planned to make his money selling puzzle software.
Q 14Which Sudoku-style arithmetic puzzle did a Japanese maths teacher invent in 2004 to sharpen his students' thinking?
KenKen
KenKen was designed to be solved without instructions, so students would learn through trial and error and independent thinking.
Q 15What 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 16Why 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 17Roughly 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 18A 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 19Euler's 'thirty-six officers' puzzle wanted no row or column to repeat an officer's rank or what?
Regiment
Regiment: no arrangement of the 36 officers is possible, yet Euler's wider guess that other sizes like it were impossible too proved wrong.
Q 20Solving 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 24Which two puzzles does the Killer variant combine?
Sudoku and Kakuro
Sudoku and Kakuro combine in a grid that often starts with no digits at all, so solvers work from each cage's sum instead.
Q 25In Killer Sudoku, which rule lets solvers pin down lone 'innie' and 'outie' cells?
The Rule of 45
The Rule of 45 works because the digits 1 to 9 always total 45, so a lone cell is 45 minus the other cages in its row, column or box.
Q 26Which Sudoku solving technique shares its name with a Star Wars spacecraft?
X-Wing
X-Wing lets solvers clear a digit from the rest of two columns once two rows confine that digit to those same columns.
Q 27What is a 3-fish pattern called in Sudoku jargon?
A swordfish
A swordfish lets solvers clear a digit from the rest of three columns once three rows confine it to those columns.
Q 28What does a Sudoku solver mean by a "proper" puzzle?
One with exactly one solution
A puzzle that needs no trial and error is called "satisfactory" instead.
Q 29Which 2020 YouTube Sudoku had its solver saying it was 'like the universe is singing to us'?
The Miracle Sudoku
The Miracle Sudoku gave the solver just two digits to start from, yet its extra rules let him fill in the whole grid.
Q 30Which common variant requires the two main diagonals to contain unique digits too?
Sudoku X
The Daily Mail's Sudoku X puzzles use 6×6 grids.