Sudoku
Sudoku is a logic puzzle where you fill a 9x9 grid with numbers 1-9 so that each row, column, and 3x3 contains every digit exactly once. No math skills required—just pattern recognition and deductive reasoning. It's satisfyingly simple to learn but offers endless challenge as puzzles increase in difficulty.
What you'll do
Solve your first easy Sudoku puzzle using scanning and elimination techniques.
What you need
Required
- Sudoku puzzle · online or printed
Start with an easy-rated puzzle from sudoku.com or a puzzle book
Nice to have
- Pencil with eraser · household
For paper puzzles; online versions have built-in notes
- Smartphone, tablet, or computer · household
For playing online or with an app
How to do it
Understand the one rule
Each row, column, and 3x3 must contain the numbers 1-9 exactly once, with no repeats. The puzzle starts with some numbers filled in as —your job is to fill the empty cells.
Scan for obvious singles
~2 minLook for rows, columns, or boxes that are missing only one or two numbers. If a row has 8 numbers filled in, the missing number goes in the empty . These easy wins build momentum.
Use crosshatching
~5 minPick a number (start with 1). Look at each 3x3 and check which rows and columns already contain that number. Where the empty cells in the box cannot have that number due to row/column conflicts, you can often find where it must go.
Use pencil marks for candidates
When a could contain multiple numbers, write small numbers in the corner. As you eliminate possibilities through scanning, erase candidates. When only one remains, that is the answer.
Work systematically through the grid
~10 minAlternate between scanning rows/columns/boxes and checking your . Each number you place gives new information. Keep going until every is filled.
Tips
Start with easy puzzles
Never guess
Focus on all three units
Use on paper
Take breaks when stuck
Glossary
- cell
- A single square in the grid where one number goes. A standard Sudoku has 81 cells (9x9).
- box
- A 3x3 section of the grid, also called a block or region. There are 9 boxes in a standard Sudoku, and each must contain 1-9.
- candidate
- A number that could potentially go in a cell based on current information. Pencil marks show candidates.
- pencil marks
- Small numbers written in cells to track which candidates remain possible. Also called notes or candidates mode in apps.
- crosshatching
- A scanning technique where you pick a number and trace rows/columns to eliminate possibilities in boxes, finding where that number must go.
- naked single
- When a cell has only one possible candidate remaining after elimination. The easiest type of solve.
- hidden single
- When a number can only go in one cell within a row, column, or box—even if that cell has other candidates.
- clues
- The numbers given at the start of the puzzle. Easy puzzles have more clues; hard puzzles have fewer.
Communities
Resources
- How to Play Sudoku for Absolute BeginnersClear 8-minute introduction covering the rules and basic solving techniques with examples
- Sudoku Rules for Complete BeginnersInteractive guide with visual examples of the four fundamental Sudoku principles
- How to Solve Sudoku Puzzles (Beginner and Advanced)Comprehensive 22-step guide progressing from basic to advanced solving techniques
Frequently asked questions
How long does it take to learn Sudoku?
You can understand the rules in 5 minutes and solve your first easy puzzle in 15-20 minutes. After completing 10-20 puzzles over a few days, most people feel comfortable with basic techniques. Mastering advanced strategies takes weeks of practice.
Do I need to be good at math to play Sudoku?
No math is required. Despite using numbers, Sudoku is purely a logic puzzle. You never add, subtract, or calculate anything—you just recognize patterns and use elimination. You could replace the numbers with letters or symbols and it would work the same way.
Is it okay to guess in Sudoku?
No, guessing is the most common beginner mistake. A wrong guess creates contradictions that often only appear when you are nearly finished, forcing you to start over. Every number placement should be provable through logic. If you are stuck, use pencil marks or try a different area of the grid.
What is the best way to play—paper or digital?
Both work well. Paper puzzles with a pencil are satisfying and portable. Digital versions (apps or websites like sudoku.com) offer unlimited free puzzles, automatic error checking, and built-in pencil mark features. Start with whichever is more convenient.
How do I know if a puzzle has only one solution?
Properly designed Sudoku puzzles always have exactly one solution. Reputable puzzle sources (major newspapers, established apps, puzzle books from known publishers) quality-check their puzzles. If a puzzle seems to have multiple solutions, it is poorly constructed.