What Is Sudoku?
Sudoku is a logic puzzle with a one-line goal: fill the grid so no number repeats in any row, column or box. Here is what that means, where the puzzle came from and why it is so addictive.
Sudoku in one paragraph
Sudoku is a number-placement logic puzzle. A standard puzzle is a 9×9 grid made of nine 3×3 boxes. Some cells are already filled in; your job is to fill the rest with the digits 1 to 9 so that every row, every column and every box contains each digit exactly once.
Despite the numbers, Sudoku has nothing to do with arithmetic. The digits are only symbols, and the puzzle works the same with letters, colors or shapes. What it tests is deduction: working out, from the clues you have, what a cell must contain.
A short history of Sudoku
- 1979: the first modern version is published in Dell Magazines in the United States as "Number Place".
- 1980s: the puzzle becomes popular in Japan, where it gets the name Sudoku, roughly "single number".
- Mid-2000s: newspapers around the world start printing a daily Sudoku, and the puzzle becomes a global favorite.
- Today: Sudoku is played in print, in apps and in the browser, and there are many variants such as smaller and larger grids and Killer Sudoku.
What the grid looks like
A classic Sudoku has 81 cells arranged in 9 rows, 9 columns and 9 boxes. The starting numbers are called givens or clues. A well-made puzzle has exactly one solution, so it can always be solved by logic without guessing.
| Part | Size | How many |
|---|---|---|
| Cell | 1 square | 81 |
| Row | 9 cells across | 9 |
| Column | 9 cells down | 9 |
| Box | 3×3 cells | 9 |
The three rules that govern these parts are explained on our Sudoku rules page.
Types of Sudoku
- By difficulty: easy, medium, hard and expert puzzles differ in how many givens there are and which techniques you need.
- By grid size: 4×4 and 6×6 grids are great for beginners and kids, while 12×12 and 16×16 grids are longer challenges.
- By extra rules: Killer Sudoku adds cages with target sums on top of the classic rules.
- By format: play online, take part in the daily puzzle, or print Sudoku for pen and paper.
Why people play Sudoku
- It is pure logic. There is no luck and no trivia, only deduction.
- It is easy to start and hard to finish. The rules take a minute to learn, but expert puzzles can take half an hour.
- It fits any moment. A puzzle can take five minutes on a break or an hour on a quiet evening.
- It is satisfying. Every correct number makes the next one easier to find.
How to start
Read the how to play Sudoku tutorial, then try an easy Sudoku. If you get stuck, the Sudoku solver can check a position, and the techniques guide shows what to look for next.
What Is Sudoku? FAQ
Is Sudoku a math puzzle?
No. Sudoku uses the digits 1 to 9 only as symbols. You never add, subtract or multiply, so no math skills are needed, only careful reasoning.
Where does the name Sudoku come from?
The name is Japanese and roughly means "single number". The puzzle was first published in the United States as "Number Place".
How many numbers are in a Sudoku?
A standard grid has 81 cells. Easy puzzles start with around 45 givens, and the hardest puzzles can have as few as 23. The proven minimum for a unique solution is 17.
Is Sudoku good for your brain?
Sudoku is a good workout for focus, working memory and logical thinking. It is a fun mental exercise, though it is not a medical treatment.
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