Home › Guides › Sudoku Rules

sudoku solvers

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 free online

sudoku solvers Sudoku competitions are held globally, where speed solvers compete to finish complex grids in the shortest time possible. andoku sudoku 3 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 solvers Basic Sudoku Rules for Beginners

uk sudoku

sudoku solvers 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. free sudoku with answers 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. free print sudoku puzzles 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. sudoku nytimes hard 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.

sudoku solvers What is Sudoku and How to Play?

sudoku variants and types

sudoku solvers 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. nyt sudoku hint 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. nyt sudoku hint 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 solvers History of the Sudoku Puzzle

sudoku book nearby

sudoku solvers Sudoku competitions are held globally, where speed solvers compete to finish complex grids in the shortest time possible. solve sudoku cube 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 sudoku cube Sudoku variants like Killer Sudoku, Jigsaw Sudoku, and Sudoku-X provide additional challenges for players looking for something different from the classic version. sudoku monster 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 solvers History of the Sudoku Puzzle

tips solving sudoku

sudoku solvers 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. blank sudoku sheet printable free 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. blank sudoku sheet printable free 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. intermediate sudoku 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. intermediate sudoku Many people enjoy solving Sudoku as a relaxing hobby. It provides a sense of accomplishment when a difficult puzzle is finally completed correctly.

sudoku solvers Common Sudoku Mistakes and How to Avoid Them

free printable hard sudoku

sudoku solvers 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. pi day sudoku answers 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. sudoku rubix cube Many people enjoy solving Sudoku as a relaxing hobby. It provides a sense of accomplishment when a difficult puzzle is finally completed correctly.

sudoku solvers How to Solve Hard Sudoku Puzzles Step by Step

sudoku for elderly

sudoku solvers 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. killer sudoku print 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.

Related Topics

how to play sudoku for beginners pdf instructions on how to play sudoku sudoku printable puzzles 4 per page algoritmo sudoku sudoku strategy for beginners pocket sudoku

🔍 Related Searches

the sudoku online toronto star sudoku sudoku solving algorithm sudoku how to do how to solve hard sudoku Naked Single Rule Sudoku Pair Strategy Sudoku X-Wing Play Easy Killer Finding Hidden Numbers Sum Sudoku Insane Killer Mode