The sudoku game is a logic puzzle played on a 9×9 grid, where you fill empty cells with the digits 1 to 9 so that every row, every column and every 3×3 box contains each number exactly once. No arithmetic or maths is required — just careful reasoning and patience.
What the Sudoku Game Actually Is
Sudoku is a single-player number-placement puzzle. The board starts with some digits already filled in — these are called "givens" or "clues" — and your job is to work out where every other digit belongs using nothing but logic.
Despite appearances, sudoku is not a maths puzzle. The digits are symbols, not values: you never add, subtract, multiply or divide. A well-made puzzle has exactly one valid solution, and every digit can be placed through deduction rather than guessing.
The standard board has 81 cells: nine rows, nine columns and nine 3×3 boxes. Each must end up containing the digits 1 to 9 with no repeats. That is the entire rulebook.
The Objective and Rules of Sudoku
The objective is straightforward: fill the grid so that every row, every column and every 3×3 box holds each digit from 1 to 9 exactly once.
The rules
- Use only the digits 1–9. No other numbers, letters or symbols appear in classic sudoku.
- Each row must contain every digit 1–9 once. No digit may repeat within a single row.
- Each column must contain every digit 1–9 once. No digit may repeat within a single column.
- Each 3×3 box must contain every digit 1–9 once. No digit may repeat within a single box.
- The givens cannot be changed. The numbers printed at the start are fixed — they are your starting clues.
- No maths required. Digits never combine or calculate; they simply need to be placed without conflict.
You don't need to be "good at maths"
Success comes from scanning, eliminating impossible placements and spotting patterns — skills closer to detective work than arithmetic. Plenty of committed solvers are indifferent mathematicians.
A Brief History of the Sudoku Game
1979: Number Place in America
The modern puzzle was most likely designed by Howard Garns, a retired architect from Connersville, Indiana, and first published in 1979 by Dell Magazines as "Number Place" (Source: Wikipedia). His name appeared in the contributor lists of issues that included it; he died in 1989, before his creation became a worldwide phenomenon.
1984: Japan gives it a name
In April 1984, Maki Kaji, president of the Japanese puzzle company Nikoli, published it in Monthly Nikolist as Sūji wa dokushin ni kagiru — "the digits must be single" — later shortened to Sudoku (Source: Wikipedia — https://en.wikipedia.org/wiki/Sudoku). In 1986 Nikoli refined the format: no more than 32 givens, placed symmetrically across the grid (Source: sudokumultiverse.com — https://sudokumultiverse.com/history-of-sudoku.html). Sudoku then became a staple of Japanese puzzle magazines.
2004–2005: The global boom
Wayne Gould, a retired New Zealand judge living in Hong Kong, spotted a puzzle in a Tokyo bookshop in 1997 and spent six years writing a program to generate unique puzzles rapidly. He persuaded The Times of London to publish them; the first daily Su Doku appeared on 12 November 2004 (Source: Wikipedia — https://en.wikipedia.org/wiki/Sudoku). Within months, newspapers across Britain, America, Australia and India were running daily grids.
Even older roots
Older roots exist — French newspapers published 9×9 number puzzles in the 1890s — but the modern 9×9-with-boxes game as we play it began with Garns (Source: Wikipedia — https://en.wikipedia.org/wiki/Sudoku).
How to Play Sudoku: A Step-by-Step Beginner's Guide
Work through your first easy puzzle like this:
- Look at the whole grid first. Find the rows, columns and boxes with the most givens — that is where your first moves will be.
- Scan for "singles". A single is a cell where only one digit can fit. In each nearly-full row, column or box, ask: which digits are missing, and where can each go?
- Use elimination. If a 7 already appears in a row, it cannot appear there again. Cross off impossible placements until only one option remains for a cell.
- Fill in confirmed digits immediately — each one is a new clue that unlocks further placements.
- Use pencil marks. When a cell could be one of several digits, jot them lightly in the corner and erase them as the picture sharpens.
- Don't guess — move on. If you're stuck, scan a different area. Well-made puzzles never require guessing; a fresh look usually reveals the move you missed.
Repeat the scan–eliminate–place cycle until all 81 cells are filled.
Sudoku Difficulty Levels
Most newspapers, books and apps grade their puzzles roughly like this:
| Level | What to expect | Solving style |
|---|---|---|
| Easy | Many givens, symmetrical layout | Basic scanning and singles will carry you through |
| Medium | Fewer givens | Needs pencil marks and systematic elimination |
| Hard | Sparse givens | Requires candidate tracking and spotting hidden patterns |
| Expert / Diabolical | Very few givens | Demands advanced techniques and long chains of reasoning |
Difficulty comes down to how many givens there are and how they are arranged (Source: sudokumultiverse.com — https://sudokumultiverse.com/history-of-sudoku.html). Stay on easy puzzles until scanning feels automatic — jumping to hard too early is why most newcomers quit.
Popular Sudoku Variants
Dozens of variants tweak the formula:
- Killer Sudoku — adds arithmetic: the digits in each irregular "cage" must sum to the labelled total. Read our dedicated killer sudoku guide.
- Diagonal (Sudoku X) — the two main diagonals must also contain the digits 1–9.
- Mini Sudoku — a 6×6 grid using digits 1–6, with 2×3 boxes. Ideal practice for children or quick games.
- Mega / 16×16 Sudoku — a 16×16 grid using digits 1–9 plus letters A–G, for serious solvers.
- Samurai Sudoku — five overlapping 9×9 grids forming one giant puzzle.
- Hyper Sudoku — adds four extra 3×3 "inner" regions that must also contain 1–9.
Sudoku vs Crossword: What's the Difference?
Sudoku and crosswords exercise different skills:
| Feature | Sudoku | Crossword |
|---|---|---|
| Core skill | Logic and pattern recognition | Vocabulary and general knowledge |
| Maths needed | None | None |
| Language needed | None — the same worldwide | Heavy — clues are language-specific |
| Learning curve | Rules take five minutes; mastery takes years | Improves steadily with vocabulary |
| Guessing | Never needed in a well-made puzzle | Common on difficult clues |
| Players | Solo | Solo, but commonly done socially |
| Completion feel | One unique solution, verified by rules | One intended solution, verified by crossings |
Sudoku's language independence helped it travel: the same grid works in London, Tokyo and Lahore.
Beginner Tips to Get You Started
- Start with the fullest rows, columns and boxes — they give up their secrets fastest.
- Place singles the moment you find them. Don't hold back confirmed digits — each one is a new clue.
- Keep pencil marks tidy. Messy candidate marks cause more mistakes than any puzzle ever will.
- Watch for rows and columns that "point at" a box — if every possible spot for a digit in a box lies on one row, it is blocked from the rest of that row.
- Take breaks. A puzzle that resists you for twenty minutes often cracks open after a cup of tea.
- Never erase in frustration. If you hit a contradiction, you made a wrong assumption somewhere — re-check your recent placements rather than guessing your way out.
Is sudoku a maths game?
No. You never perform arithmetic; the digits are nine distinct symbols, which is why the same puzzle works identically in every language.
Who invented sudoku?
The modern 9×9 sudoku was most likely created by Howard Garns, a retired American architect, and first published in 1979 as “Number Place”. It got its name later in Japan, where Maki Kaji’s Nikoli popularised it (Source: Wikipedia — https://en.wikipedia.org/wiki/Sudoku).
What does “sudoku” mean?
From the Japanese *Sūji wa dokushin ni kagiru*, “the numbers must be single” — each digit appears once per row, column and box. *Sudoku* abbreviates the phrase (Source: sudokumultiverse.com — https://sudokumultiverse.com/history-of-sudoku.html).
How long does it take to solve a sudoku puzzle?
It depends on difficulty and experience. An easy puzzle may take a beginner fifteen to twenty minutes; an expert-level puzzle can occupy a strong solver for an hour or more. Speed comes naturally with practice.
Can a sudoku puzzle have more than one solution?
A properly constructed sudoku has exactly one unique solution — that’s part of what makes it fair. Cheaply generated puzzles occasionally have multiple solutions, which is why reputable publishers test every grid before printing it. See our guide to [sudoku puzzle books](https://plusword.co.uk/sudoku-puzzle-books/) for hand-checked grids.
Do you have to guess to solve hard sudoku?
No. Every well-made sudoku is solvable by pure logic. If you find yourself guessing, either the puzzle is badly made or you haven’t learned the technique that cracks it.
Are there sudoku competitions?
Yes. The [World Sudoku Championship](https://en.wikipedia.org/wiki/World_Sudoku_Championship), organised by the World Puzzle Federation, has been held annually since 2006 — proof that this quiet little grid game became a serious competitive sport.