Sudoku91Sudoku91

How to Play Sudoku: A Complete Beginner's Guide

Sudoku is one of the world's most popular logic puzzles - and it requires absolutely no math. Whether you have never touched a Sudoku grid before or you want a clear refresher, this guide walks you through everything you need to know to start solving puzzles with confidence.

What Is Sudoku?

Sudoku is a number-placement puzzle played on a 9×9 grid divided into nine 3×3 boxes (also called regions or blocks). The goal is simple: fill every empty cell with a digit from 1 to 9 so that each row, each column, and each 3×3 box contains every digit exactly once.

The puzzle was popularized in Japan in the 1980s - the name "Sudoku" comes from the Japanese phrase "sūji wa dokushin ni kagiru," meaning "the digits must remain single." Today, millions of people solve Sudoku puzzles daily in newspapers, apps, and on websites like Sudoku91.

Despite using numbers, Sudoku is purely a logic puzzle. You could replace the digits with letters, colors, or symbols and the puzzle would work exactly the same way. No arithmetic is involved - only deduction and elimination.

Understanding the Sudoku Grid

A standard Sudoku grid has 81 cells arranged in 9 rows and 9 columns. The grid is further divided into nine 3×3 boxes, separated by thicker lines.

↔ Row - A horizontal line of 9 cells running left to right across the grid. There are 9 rows total.
↕ Column - A vertical line of 9 cells running top to bottom. There are 9 columns total.
▣ Box (Region) - A 3×3 group of 9 cells outlined by thicker borders. There are 9 boxes total.

When a puzzle starts, some cells are already filled with digits. These are called "givens" or "clues." The number of givens determines the puzzle's difficulty - easy puzzles have more givens (36-45), while evil puzzles have very few (17-22).

The Three Rules of Sudoku

Every Sudoku puzzle follows exactly three rules. If you remember these, you know everything you need to get started:

Rule 1: Each row must contain the digits 1 through 9, with no repeats

Look at any horizontal row in the grid. When the puzzle is complete, that row will contain each of the digits 1, 2, 3, 4, 5, 6, 7, 8, and 9 exactly once.

Rule 2: Each column must contain the digits 1 through 9, with no repeats

The same rule applies vertically. Every column from top to bottom must have all nine digits with no duplicates.

Rule 3: Each 3×3 box must contain the digits 1 through 9, with no repeats

Each of the nine 3×3 boxes (outlined by thicker borders) must also contain all nine digits exactly once. This is the constraint that makes Sudoku uniquely challenging.

How to Solve a Sudoku Puzzle: Step by Step

Follow these steps to solve your first Sudoku puzzle. We will start with the simplest techniques that work on easy and medium puzzles.

1

Step 1: Scan the Grid

Before placing any digit, take a moment to scan the entire grid. Look for rows, columns, or boxes that are nearly complete - these are the easiest places to find a solution. If a row has 8 of 9 digits filled in, the missing digit is the answer for the empty cell.

2

Step 2: Use Cross-Hatching

Pick a digit (say, 1) and scan each 3×3 box to see where that digit can go. Look at the rows and columns that pass through the box - if a row or column already contains that digit, it eliminates cells in the box. When only one cell remains, that is where the digit goes.

3

Step 3: Apply the Last Remaining Cell Technique

If a row, column, or box has only one empty cell left, the missing digit is the only possibility. Fill it in immediately. This often triggers a chain reaction - filling one cell may leave another group with only one remaining.

4

Step 4: Use Pencil Marks (Notes)

For cells where multiple digits are possible, write small candidate numbers (pencil marks) in the cell. On Sudoku91, toggle Notes mode to do this. As you fill in digits elsewhere, come back and eliminate candidates that are no longer possible.

5

Step 5: Look for Naked Singles

A naked single is a cell where only one candidate remains after elimination. Check your pencil marks - when a cell has been reduced to a single candidate, that digit is the answer. Fill it in and update surrounding pencil marks.

6

Step 6: Find Hidden Singles

A hidden single occurs when a digit can only go in one cell within a row, column, or box - even if that cell has multiple candidates. For example, if the digit 7 can only go in one cell within a particular row, it must go there regardless of what other candidates that cell has.

7

Step 7: Repeat and Solve

Continue scanning, cross-hatching, and checking for singles until the entire grid is filled. For easy and medium puzzles, these techniques are usually sufficient to reach the solution.

Common Mistakes Beginners Make

Guessing instead of deducing

Every Sudoku puzzle with a unique solution can be solved through pure logic. If you feel like guessing, you have likely missed an elimination somewhere. Step back and re-scan the grid.

Forgetting to update pencil marks

When you place a digit, remember to remove that digit from the pencil marks in the same row, column, and box. Stale pencil marks lead to confusion and errors.

Focusing on one area too long

If you are stuck in one section of the grid, move to a different area. Progress elsewhere often unlocks cells you were stuck on earlier.

Tips for Sudoku Beginners

Ready to Play?

Now that you know the rules and basic techniques, put your knowledge into practice. Start with an easy puzzle and work your way up as your skills improve.

Play Sudoku Now

FAQ

Do you need to be good at math to play Sudoku?
No. Sudoku uses numbers as symbols, but no arithmetic is involved. It is purely a logic and deduction puzzle. You could replace the digits with letters or shapes and the puzzle would work identically.
How long does it take to solve a Sudoku puzzle?
It depends on the difficulty and your experience. Beginners might take 15-30 minutes on an easy puzzle, while experienced solvers can complete one in under 5 minutes. Hard and expert puzzles can take 30-60 minutes or more.
What if I get stuck on a Sudoku puzzle?
Take a break and come back with fresh eyes. Re-scan the entire grid systematically. Check for hidden singles you may have missed. On Sudoku91, your progress is auto-saved, so you can return anytime.
Is there always only one solution to a Sudoku puzzle?
A properly constructed Sudoku puzzle has exactly one unique solution. All puzzles on Sudoku91 are validated to ensure they have a single solution that can be reached through logic alone.