The history of Sudoku

Before Sudoku: Latin squares and French newspapers

The mathematical skeleton of Sudoku is the Latin square — an n×n grid where each symbol appears once per row and column — studied systematically by Leonhard Euler in the 1780s. Sudoku adds one extra constraint, the 3×3 box, and that single addition is what turns a mathematical object into a puzzle.

Puzzle versions appeared earlier than most people assume. French newspapers in the 1890s printed number puzzles on 9×9 grids with sub-squares, close enough to modern Sudoku to be recognisable, though usually using arithmetic and sometimes double-digit numbers. They disappeared around the First World War and had no direct descendants.

1979: Howard Garns and Number Place

Modern Sudoku was invented by Howard Garns, a retired architect from Indianapolis, and published in 1979 by Dell Magazines under the name Number Place. Garns's contribution was the exact form we use: a 9×9 grid, 3×3 boxes, symmetric clue placement, and a unique solution reachable by logic.

He was not credited. Dell did not name its puzzle contributors, and Garns's authorship was only established later by researchers comparing issues in which the puzzle did and did not appear. He died in 1989, before the puzzle bore his name anywhere, and before it became one of the most played puzzles in the world.

Japan: the puzzle gets its name

In 1984 the Japanese puzzle publisher Nikoli picked up Number Place and printed it as 数独 — sūdoku, short for a phrase meaning "the digits must be single" or "unmarried numbers". Nikoli's editor Maki Kaji is usually credited with the name.

Nikoli also added the two conventions that define a good modern puzzle:

• No more than 32 clues, keeping puzzles genuinely challenging.
• Symmetrical clue placement, which is purely aesthetic and is now near-universal.

Crucially, Nikoli's puzzles were hand-made by constructors, which is why Japanese Sudoku of that era has a reputation for elegance: a human chose which deductions the solver would have to find, and in which order.

2004–2005: the global craze

Sudoku became a worldwide phenomenon because of one person: Wayne Gould, a retired Hong Kong judge from New Zealand who found the puzzle in a Tokyo bookshop in 1997, spent six years writing a program to generate puzzles, and then persuaded The Times of London to print one in November 2004.

What followed was one of the fastest media crazes on record. Within months Sudoku was in nearly every British newspaper, then across Europe, North America and Australia. By 2005 it was in books, on phones, on television, and being blamed for lost productivity in a genre of news story that recurs every decade with a different cause.

The reasons it spread so fast are worth noting: it needs no language, so the same puzzle works in every country; it needs no equipment beyond a pencil; and difficulty can be graded precisely, so publishers could serve beginners and experts from the same generator.

The mathematics that followed

Sudoku turned out to be a good research problem, and the results arrived quickly once people started asking.

• 2005: Bertram Felgenhauer and Frazer Jarvis counted the completed grids — 6,670,903,752,021,072,936,960 — reducing to about 5.47 billion essentially different ones once symmetries are accounted for.
• 2012: Gary McGuire, Bastian Tugemann and Gilles Civario proved the 17-clue minimum by exhaustive search, a computation that took the equivalent of years of processor time.
• Complexity: generalised Sudoku on an n²×n² grid is NP-complete, which is the formal statement of what solvers feel on a hard puzzle.

The variant scene has since become its own culture, with setters publishing puzzles built around a single elegant deduction and solvers filming themselves working through them. It is arguably the healthiest state the puzzle has been in since 2005.

Common questions