Home › Guides › Sudoku Rules

rules

The Basics

Sudoku is a logic-based number puzzle that has become one of the world's most popular brain games. Despite using numbers, no math is required—only logical deduction and pattern recognition.

The goal is simple: fill a 9×9 grid with digits 1-9 following three basic rules. Each puzzle has a unique solution that can be reached through logic alone—never guessing.

💡 Key Fact

The name "Sudoku" comes from Japanese, meaning "single numbers" (数独, sūdoku). However, the modern puzzle was actually invented by an American architect, Howard Garns, in 1979.

The Three Rules

Every Sudoku puzzle follows exactly three rules:

1

Each Row Contains 1-9

Every horizontal row must contain each digit from 1 to 9 exactly once. No repetition allowed.

2

Each Column Contains 1-9

Every vertical column must contain each digit from 1 to 9 exactly once. No repetition allowed.

3

Each 3×3 Box Contains 1-9

Each of the nine 3×3 sub-grids (boxes) must contain each digit from 1 to 9 exactly once.

✅ Pro Tip

Think of it this way: every row, column, and box is like a container that needs exactly one of each number 1-9. If a number already exists in that container, it can't appear again.

Understanding the Grid

A standard Sudoku grid consists of:

  • 81 cells arranged in a 9×9 grid
  • 9 rows running horizontally
  • 9 columns running vertically
  • 9 boxes (3×3 sub-grids) outlined by thicker lines
534678912 672195348 198342567 859761423 426853791 713924856 961537284 287419635 345286179

Blue numbers are given clues; gray numbers are solved by the player

How to Start Solving

Follow these steps when approaching a new puzzle:

  1. Scan the grid - Look for rows, columns, or boxes that have many given numbers
  2. Find obvious placements - If a row/column/box is missing only one number, fill it in
  3. Use elimination - For each empty cell, determine which numbers are possible
  4. Look for singles - Find cells where only one number can go
  5. Repeat - Keep scanning and eliminating until the puzzle is complete

Basic Techniques

1. Scanning (Crosshatching)

Look at each number (1-9) and scan where it can go in empty boxes. Use the existing numbers in rows and columns to eliminate possibilities.

2. Naked Singles

When a cell has only one possible candidate after eliminating all numbers that appear in its row, column, and box, that candidate must go there.

3. Hidden Singles

When a number can only go in one cell within a row, column, or box—even if that cell has other candidates—that number must go there.

Tips for Beginners

✅ Do's

• Start with easy puzzles and gradually increase difficulty
• Use pencil marks to note possible candidates
• Take breaks when stuck—fresh eyes help
• Double-check each number placement

⚠️ Don'ts

• Never guess—Sudoku is pure logic
• Don't place a number unless you're 100% sure
• Avoid the temptation to look at solutions
• Don't give up—every puzzle has a solution

Frequently Asked Questions

Do I need to be good at math?

No! Sudoku uses numbers as symbols, but requires no mathematical calculations. You could use letters, colors, or shapes instead.

Can a Sudoku puzzle have multiple solutions?

A properly constructed Sudoku puzzle has exactly one unique solution. If a puzzle has multiple solutions, it's considered flawed.

Is guessing ever necessary?

Never. Every valid Sudoku puzzle can be solved through pure logic. If you feel the need to guess, you may have missed a logical deduction.

killer sudoku krazydad

rules Sudoku competitions are held globally, where speed solvers compete to finish complex grids in the shortest time possible.

rules What is Sudoku and How to Play?

leetcode sudoku solver

rules There are several difficulty levels in Sudoku, ranging from easy for beginners to expert for seasoned players. Solving techniques include scanning, cross-hatching, and identifying candidate numbers. sudoku color cube To solve a Sudoku puzzle, one must look for cells where only one number is possible, or rows/columns/blocks where a specific number has only one possible placement.

rules The Benefits of Playing Sudoku Daily

sudoku near me

rules The rules of Sudoku are simple but the depth of the game is immense. Every well-posed Sudoku puzzle has a unique solution that can be reached through logical deduction. mega sudoku 16x16 Modern Sudoku was popularized by Nikoli in Japan in the 1980s. It has since become a global phenomenon, with daily puzzles appearing in newspapers and online platforms worldwide. extremely easy sudoku Playing Sudoku daily has many cognitive benefits, including improving memory, concentration, and logical reasoning skills. It is a great way to keep the brain active and healthy. sudoku wooden board game Playing Sudoku daily has many cognitive benefits, including improving memory, concentration, and logical reasoning skills. It is a great way to keep the brain active and healthy. free printable easy sudoku Many people enjoy solving Sudoku as a relaxing hobby. It provides a sense of accomplishment when a difficult puzzle is finally completed correctly.

rules Sudoku Strategies: Scanning and Marking

sudoku books

rules Advanced Sudoku solving methods involve complex patterns like X-Wing, Swordfish, and XY-Wing. These techniques are often required for hard and expert level puzzles. killer sudoku free The rules of Sudoku are simple but the depth of the game is immense. Every well-posed Sudoku puzzle has a unique solution that can be reached through logical deduction. marty's daily sudoku Playing Sudoku daily has many cognitive benefits, including improving memory, concentration, and logical reasoning skills. It is a great way to keep the brain active and healthy. free online sudoku very hard Sudoku variants like Killer Sudoku, Jigsaw Sudoku, and Sudoku-X provide additional challenges for players looking for something different from the classic version.

rules What is Sudoku and How to Play?

sudoku new york times

rules Playing Sudoku daily has many cognitive benefits, including improving memory, concentration, and logical reasoning skills. It is a great way to keep the brain active and healthy. solve any sudoku puzzle Playing Sudoku daily has many cognitive benefits, including improving memory, concentration, and logical reasoning skills. It is a great way to keep the brain active and healthy. sudoku slver Advanced Sudoku solving methods involve complex patterns like X-Wing, Swordfish, and XY-Wing. These techniques are often required for hard and expert level puzzles. sudoku vs Sudoku is a logic-based, combinatorial number-placement puzzle. The objective is to fill a 9x9 grid with digits so that each column, each row, and each of the nine 3x3 subgrids contain all of the digits from 1 to 9. sudoku slver Many people enjoy solving Sudoku as a relaxing hobby. It provides a sense of accomplishment when a difficult puzzle is finally completed correctly.

rules The Benefits of Playing Sudoku Daily

5 grid sudoku

rules Sudoku is a logic-based, combinatorial number-placement puzzle. The objective is to fill a 9x9 grid with digits so that each column, each row, and each of the nine 3x3 subgrids contain all of the digits from 1 to 9. beginner easy sudoku printable Playing Sudoku daily has many cognitive benefits, including improving memory, concentration, and logical reasoning skills. It is a great way to keep the brain active and healthy. beginner easy sudoku printable Sudoku competitions are held globally, where speed solvers compete to finish complex grids in the shortest time possible.

rules How to Solve Hard Sudoku Puzzles Step by Step

sudoku 6 6

rules Sudoku is a logic-based, combinatorial number-placement puzzle. The objective is to fill a 9x9 grid with digits so that each column, each row, and each of the nine 3x3 subgrids contain all of the digits from 1 to 9. extreme sudoku book Advanced Sudoku solving methods involve complex patterns like X-Wing, Swordfish, and XY-Wing. These techniques are often required for hard and expert level puzzles.

Related Topics

ny times games sudoku samurai sudoku print new york times sudoku medium daily diagonal sudoku sudoku algorithms sudoku arkadium daily

🔍 Related Searches

sudoku free printable medium online samurai sudoku mini sudoku book easy sudoku puzzles by krazydad volume 1 book 1 next time try reading the clue or stick to sudoku Evil Sudoku Last Remaining Cell Medium Killer Sudoku Play Sudoku Online Advanced Killer Advanced Basic Tip Sudoku Hidden Single