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Sudoku facts: history, math and records

Short, checked facts about the puzzle, each with a link to where it comes from.

Updated 2026-10-05

History

  1. Modern Sudoku first appeared in the United States in 1979. Dell Magazines first published the puzzle in 1979 under the name Number Place. It was most likely made by Howard Garns, a retired architect and freelance puzzle maker from Indiana.

    Source: Wikipedia: Sudoku

  2. Nikoli introduced it in Japan in 1984. The puzzle company Nikoli brought it to Japan in 1984 as Sūji wa dokushin ni kagiru, roughly “the digits must be single”. The name was later shortened to Sudoku: su means number and doku means single.

    Source: Nikoli: Sudoku, Wikipedia: Sudoku

  3. In Japan it is often called Nanpure. Sudoku is a Nikoli trademark in Japan, so other Japanese publishers call the puzzle Number Place, often shortened to Nanpure.

    Source: Nikoli: Sudoku, Wikipedia: Sudoku

  4. Symmetry was a house rule. In 1986 Nikoli decided that the printed numbers in its puzzles must sit in a symmetrical pattern.

    Source: Nikoli: Sudoku

  5. A London newspaper helped make it a worldwide hit in 2004. The Times in London began printing Wayne Gould's puzzles on 12 November 2004. Gould, a retired judge in Hong Kong, had spent six years writing a program that makes them.

    Source: Wikipedia: Sudoku

  6. French newspapers printed close relatives in the 1890s. Le Siècle printed a partly filled 9×9 magic square with 3×3 squares in 1892, and La France printed a puzzle in 1895 that it called a diabolical magic square.

    Source: Wikipedia: Sudoku

Math

  1. Every finished 9×9 Sudoku is a Latin square. In a Latin square, each row and each column holds every symbol once. Sudoku adds one rule: each 3×3 box holds all nine digits too. Leonhard Euler studied Latin squares in the 18th century.

    Source: Wikipedia: Latin square

  2. A 9×9 grid can be completed in 6,670,903,752,021,072,936,960 ways. That is how many completely and correctly filled 9×9 grids exist, about 6.67 × 10²¹. Bertram Felgenhauer and Frazer Jarvis counted them in 2005.

    Source: Felgenhauer and Jarvis, Enumerating possible Sudoku grids (2005), OEIS A107739: number of Sudoku grids

  3. About 5.5 billion of them are essentially different. Count two grids as the same when one turns into the other by relabelling the digits, rotating, reflecting, or reordering rows and columns in the ways that keep a grid valid (rows within a band, whole bands, columns within a stack, whole stacks), and 5,472,730,538 different grids remain. Ed Russell and Frazer Jarvis computed this.

    Source: Wikipedia: Mathematics of Sudoku

  4. A 9×9 puzzle needs at least 17 printed numbers. With 16 or fewer, no standard 9×9 Sudoku has exactly one answer. Gary McGuire, Bastian Tugemann and Gilles Civario showed this with an exhaustive computer search and announced it in January 2012. Seventeen is the minimum, not a guarantee: 17 printed numbers alone do not make the answer unique. Sudoku checker →

    Source: McGuire, Tugemann and Civario, There is no 16-Clue Sudoku (arXiv 1201.0749)

  5. Mini Sudoku has far fewer finished grids. There are 288 finished 4×4 Sudoku grids with 2×2 boxes, and 28,200,960 finished 6×6 grids with boxes of 2 rows by 3 columns. Sudoku for kids →

    Source: OEIS A291187: number of 2×n Sudoku grids

  6. Sudoku in general is a famously hard problem. For Sudoku grids that can grow without limit (n²×n² with n×n boxes), deciding whether a partly filled grid can be completed is NP-complete. Takayuki Yato and Takahiro Seta published this result in 2003.

    Source: Wikipedia: Mathematics of Sudoku

Competitions

  1. The first World Sudoku Championship was in 2006. It was held in Lucca, Italy, and won by Jana Tylová of the Czech Republic. The championship is organised by a member of the World Puzzle Federation.

    Source: Wikipedia: World Sudoku Championship

In our app

  1. The number of clues does not set the level. In the 60,000 puzzles in our app, Expert, Master and Extreme puzzles start from the same range of clues (26 to 30, usually 26), yet each level needs a different family of techniques. What each Sudoku difficulty level asks of you →

    Source: What each Sudoku difficulty level asks of you

Sources

See also

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