How to Play Sudoku: A Complete Beginner's Guide
Quick Summary
Sudoku is a logic puzzle where you fill a 9x9 grid so that every row, column, and 3x3 box contains the numbers 1-9 exactly once. No math required — just logic and patience. This guide will take you from zero to confidently solving puzzles.
What is Sudoku?
Sudoku (Japanese for "single number") is the world's most popular logic puzzle. It was first published in a US magazine in 1979 under the name "Number Place" and later became a global phenomenon after gaining popularity in Japan in the 1980s. Today, millions of people solve Sudoku puzzles every day — in newspapers, online, and on mobile apps.
Despite using numbers, Sudoku is not a math puzzle. It is a pure logic game. You never need to add, subtract, or perform any calculations. The numbers 1 through 9 are simply symbols — you could replace them with letters, colors, or shapes and the puzzle would work identically.
A standard Sudoku puzzle consists of a 9x9 grid divided into nine 3x3 boxes (also called blocks or regions). Some cells are pre-filled with numbers — these are your clues. Your job is to fill in the remaining empty cells following three simple rules.
Total cells in the grid
3x3 boxes in the grid
Minimum clues given
The Rules of Sudoku
Sudoku has only three rules. They are simple to understand but create endlessly complex and satisfying puzzles. Every placement you make must satisfy all three rules simultaneously.
Row Rule
Each of the 9 horizontal rows must contain every number from 1 to 9 exactly once. No duplicates allowed in any row.
Column Rule
Each of the 9 vertical columns must contain every number from 1 to 9 exactly once. No duplicates allowed in any column.
Box Rule
Each of the 9 outlined 3x3 boxes must contain every number from 1 to 9 exactly once. No duplicates allowed in any box.
That's it — three rules! The beauty of Sudoku is that these simple constraints create rich, intricate logic that scales from easy 2-minute puzzles to fiendishly hard challenges that take hours. For a deeper dive into the rules and variants, see our complete Sudoku rules guide.
How to Solve Sudoku Step by Step
Solving Sudoku is all about elimination. For each empty cell, you figure out which numbers are impossible (because they already appear in the same row, column, or box) and narrow down what's left. Here are the five fundamental steps every beginner should master:
Scan for Obvious Numbers
Start by scanning each row, column, and 3x3 box. If eight of the nine numbers are already placed, the ninth number must go in the remaining empty cell. This is called the Last Free Cell technique and is the simplest way to fill in numbers.
Use Crosshatching
Crosshatching is the most important scanning technique for beginners. Pick a number (say 7) and look at a 3x3 box where 7 hasn't been placed yet. Check which rows and columns passing through that box already contain a 7. This eliminates cells where 7 cannot go. If only one cell remains, place the 7 there.
Tip: Crosshatching works best when you focus on one number at a time. Start with numbers that appear most frequently in the grid — they'll have fewer possible positions left.
Look for Naked Singles
A Naked Single occurs when an empty cell has only one possible candidate. Check the cell's row, column, and box — if eight different numbers already appear across these three units, the ninth number must go in that cell. This is one of the most fundamental and frequently used solving techniques.
Use Pencil Marks
When you can't immediately determine a cell's value, write small candidate numbers (called pencil marks or notes) inside the cell. For each empty cell, list every number that isn't already in its row, column, or box. As you solve more cells, come back and update your pencil marks by removing eliminated candidates.
Pro tip: On Sudoku247, toggle notes mode to automatically manage pencil marks. Our AI hint system uses your pencil marks to suggest the next logical step.
Apply Elimination
Once you have pencil marks in place, look for Hidden Singles. Even if a cell has multiple candidates, check if any of those candidates appear in only that one cell within its row, column, or box. If a number can only go in one place within a unit, it must go there — regardless of what other candidates the cell has.
These five steps will carry you through easy and most medium puzzles. For harder puzzles, you'll need advanced techniques like Naked Pairs, X-Wing, and Y-Wing. Explore our full techniques library to level up your skills.
Beginner Mistakes to Avoid
Every Sudoku beginner makes the same mistakes at first. Being aware of these common pitfalls will save you frustration and help you develop good solving habits from the start.
1. Guessing Instead of Using Logic
The most common mistake is placing a number because it "feels right" without verifying it logically. Every valid Sudoku puzzle has a unique solution that can be reached through pure logic. If you find yourself guessing, stop and look for a cell where you can make a certain deduction. Guessing leads to contradictions that are hard to backtrack, especially without an undo button. Build the discipline of only placing numbers you can prove are correct.
2. Forgetting to Check All Three Constraints
New players often check whether a number conflicts with the row and column but forget about the 3x3 box — or vice versa. Every single placement must satisfy all three rules simultaneously: the row, the column, and the box. Make it a habit to triple-check every number before you commit it. A single wrong placement can cascade into multiple errors that are painful to untangle later.
3. Not Using Pencil Marks
Many beginners try to solve puzzles entirely in their head, avoiding pencil marks because they seem tedious. This works for easy puzzles, but as difficulty increases, keeping track of candidates mentally becomes impossible. Pencil marks are not training wheels — they are a core tool used by every expert solver. Start using them early and you'll find medium and hard puzzles far more approachable.
4. Staring at One Area Too Long
When you get stuck on a particular row, column, or box, it's tempting to keep staring at it hoping the answer will appear. Instead, move to a completely different area of the grid. Solving other cells often reveals new information that makes your stuck area solvable. The best Sudoku solvers constantly rotate their attention across the entire grid rather than fixating on one spot.
5. Not Updating Pencil Marks After Placements
When you place a number, you must update your pencil marks by removing that number from all cells in the same row, column, and box. Forgetting this step means your pencil marks become stale and unreliable, leading to missed deductions or incorrect placements. On Sudoku247, our auto-notes feature handles this for you — but when solving on paper, develop the habit of updating notes immediately after each placement.
Common Sudoku Strategies
Beyond the basic five steps, Sudoku has a rich library of solving techniques organized by difficulty. Here's a roadmap of the strategies you'll encounter as you progress from beginner to expert. Each technique builds on the ones before it, so learn them in order for the smoothest progression.
BeginnerFoundation Techniques
These techniques are enough to solve most easy puzzles. They focus on finding cells where only one number is possible.
IntermediateCandidate Elimination
These techniques don't directly place numbers — instead, they eliminate candidates from pencil marks, which indirectly reveals naked and hidden singles. Essential for medium-difficulty puzzles.
AdvancedPattern Recognition
These powerful techniques involve spotting geometric patterns across the grid. Required for hard and expert puzzles. They take practice to spot consistently, but they're immensely satisfying once mastered.
Want to go deeper? Our complete techniques library covers all 13+ techniques with interactive examples, step-by-step explanations, and practice puzzles for each one.
Solving Strategy at a Glance
Ready to Start Playing?
The best way to learn Sudoku is by doing. Start with an easy puzzle to practice scanning and crosshatching, then work your way up as you build confidence.
Frequently Asked Questions
Q: How long does it take to learn Sudoku?
A: Most beginners can learn the basic rules in 5 minutes and start solving easy puzzles right away. Developing speed and mastering advanced techniques takes weeks to months of regular practice.
Q: Do I need to be good at math to play Sudoku?
A: No! Sudoku is a logic puzzle, not a math puzzle. The numbers 1-9 are just symbols — you could replace them with letters or colors and the game would work the same way.
Q: Is guessing allowed in Sudoku?
A: No. Every well-formed Sudoku puzzle can be solved using logic alone. If you feel stuck, look for techniques you haven't tried yet rather than guessing.
Q: What are pencil marks in Sudoku?
A: Pencil marks (also called candidates or notes) are small numbers written in a cell to track which values are still possible for that cell. They are essential for solving medium and harder puzzles.
Q: How many clues does a Sudoku puzzle start with?
A: A standard Sudoku puzzle typically has between 17 and 35 given clues. The minimum number of clues for a unique solution is 17. Fewer clues generally means a harder puzzle.
Q: What is crosshatching in Sudoku?
A: Crosshatching is a scanning technique where you look at a row or column to see where a specific number can go within a 3x3 box. It is one of the most fundamental solving methods for beginners.
Q: Can a Sudoku puzzle have more than one solution?
A: A properly constructed Sudoku puzzle has exactly one unique solution. If a puzzle has multiple solutions, it is considered invalid.
Q: What should I do if I get stuck on a Sudoku puzzle?
A: Try a different technique, double-check your pencil marks for errors, or focus on a different area of the grid. You can also use our AI-powered hint system for step-by-step guidance.
Q: What is the difference between easy and hard Sudoku puzzles?
A: Easy puzzles have more given clues (typically 36-45) and can be solved using basic techniques like scanning and naked singles. Hard and expert puzzles have fewer clues (22-27) and require advanced techniques like X-Wing, Swordfish, and Y-Wing to solve.
Q: How can I get faster at solving Sudoku?
A: Practice regularly, learn to recognize patterns quickly, use pencil marks efficiently, and work through puzzles at progressively harder difficulties. Speed comes naturally as techniques become second nature. Try our daily puzzle to build a consistent practice habit.
Continue Learning
Sudoku Rules
Deep dive into the complete rules, variants, and advanced clarifications.
All Techniques
Explore 13+ solving techniques from beginner to expert level.
Daily Puzzle
Practice daily with a fresh puzzle. Build a solving streak!
Printable Puzzles
Download free PDF puzzles to practice offline with pencil and paper.