How to Play Sudoku: Complete Beginner's Guide

Sudoku is a logic puzzle played on a 9x9 grid divided into nine 3x3 boxes. Your goal is simple: fill every empty cell with a number from 1 to 9 so that each row, each column, and each 3x3 box contains every number exactly once. No math is required — sudoku is pure logic, pattern recognition, and deduction. A standard puzzle starts with some cells already filled in (called "givens"), and your job is to figure out the rest. Every valid sudoku puzzle has exactly one solution, meaning you should never need to guess.

The Three Rules of Sudoku

Sudoku has only three rules, and they are all variations of the same idea: no repeats allowed.

1. Each row must contain the numbers 1 through 9 exactly once. Look at any horizontal row across the grid. When the puzzle is complete, you will see each digit from 1 to 9 appearing once and only once in that row.
2. Each column must contain the numbers 1 through 9 exactly once. The same rule applies vertically. Every column running from top to bottom must have all nine digits without repetition.
3. Each 3x3 box must contain the numbers 1 through 9 exactly once. The grid is divided into nine smaller boxes (sometimes called "blocks" or "regions"). Each of these boxes must also contain all digits from 1 to 9.

That is it. There are no additional rules about diagonals, no arithmetic, and no special operations. If you can count to nine, you can play sudoku. The challenge comes entirely from applying these three simple rules to deduce which number belongs in each cell.

Understanding the Grid

Before you place your first number, take a moment to understand the anatomy of a sudoku grid. The full grid is 9 cells wide and 9 cells tall, giving you 81 cells total. These cells are organized into:

• 9 rows — horizontal lines labeled Row 1 (top) through Row 9 (bottom)
• 9 columns — vertical lines labeled Column 1 (left) through Column 9 (right)
• 9 boxes — the 3x3 regions marked by thicker borders on the grid

Every cell sits at the intersection of exactly one row, one column, and one box. This means every cell is constrained by three groups simultaneously. When you place a number in a cell, it must satisfy all three constraints — it cannot already appear in that cell's row, column, or box.

The cells that already have numbers when you start the puzzle are called givens or clues. A typical easy puzzle might have 35 to 40 givens, while a hard puzzle might have as few as 22 to 27. The fewer the givens, the more deduction you need to solve the puzzle — though the number of givens alone does not determine difficulty.

Solving Your First Puzzle: Step by Step

Let us walk through the thought process of solving a sudoku puzzle from scratch. You do not need a specific puzzle in front of you — these steps apply universally.

Step 1: Scan the Grid

Start by scanning the entire grid to get oriented. Look for rows, columns, or boxes that already have many numbers filled in. The more numbers a group already has, the fewer possibilities remain for the empty cells. A row with seven numbers filled in only needs two more — those are your easiest targets.

Do a quick count: which numbers appear most frequently across the grid? If the number 7 appears seven times already, there are only two more 7s to place. This gives you a focused search — check the two rows, two columns, or two boxes still missing a 7.

Step 2: Look for Naked Singles

A naked single is the simplest solving technique. Look at any empty cell and check what numbers already appear in its row, column, and box. If eight of the nine digits are already present across those three groups, only one number can go in that cell. Place it confidently.

For example, if an empty cell's row contains 1, 2, 3, 5, 7, 8 and its column adds 4 and 9 to the exclusion list, the only remaining digit is 6. That cell must be 6. This is the most basic deduction in sudoku, and on easy puzzles, you can solve a surprising number of cells this way.

Step 3: Use Scanning (Cross-Hatching)

Scanning (also called cross-hatching) is the technique most beginners learn first. Pick a number — say 5 — and look at where it already appears on the grid. For each box that does not yet contain a 5, look at the rows and columns passing through that box. The existing 5s in those rows and columns eliminate certain cells within the box. If only one cell remains where the 5 can go, you have found its position.

Work through each number from 1 to 9 systematically. Some solvers start with whichever number appears most often (since fewer placements remain), while others always go in order. Either approach works — the key is being thorough.

Step 4: Check Each Box

After scanning individual numbers, shift your focus to individual boxes. For each 3x3 box, list the missing numbers. Then, for each missing number, determine which empty cells in the box could hold it. Often, row and column constraints narrow the options to a single cell.

This is essentially the same logic as scanning, but approached from the box's perspective rather than the number's perspective. Both approaches find the same placements, but switching between them helps you catch things you might have missed.

Step 5: Repeat and Cascade

Every number you place creates new constraints that may reveal additional cells. Placing a 5 in a row means that row no longer needs a 5 — but it also affects the column and box containing that cell. Always check whether a new placement immediately reveals another one nearby.

On easy puzzles, this cascading effect means that once you get rolling, cells can fall like dominoes. You place one number, which reveals another, which reveals another. This satisfying chain reaction is one of the things that makes sudoku so compelling.

Basic Techniques Every Beginner Needs

Naked Singles

As described above, a naked single occurs when only one digit can possibly go in a cell. This is your bread-and-butter technique for easy puzzles. Get comfortable checking a cell's row, column, and box quickly, and you will spot naked singles in seconds. For more on this foundational technique, see our guide to hidden singles, which covers both naked and hidden singles in detail.

Hidden Singles

A hidden single is when a number can only go in one cell within a particular row, column, or box — even though that cell might have multiple candidates overall. For example, if you are looking at a box and the number 3 can only fit in one cell of that box (because all other empty cells in the box have 3 eliminated by their row or column), then 3 must go there — regardless of what other numbers could also go in that cell.

Hidden singles are perhaps the single most important technique in sudoku. They solve more cells than any other method, and learning to spot them quickly is the key to moving beyond beginner puzzles.

Scanning Rows and Columns

As you gain experience, scanning becomes faster and more intuitive. Instead of methodically checking every row and column for a given number, you will start to see patterns at a glance. Your eyes will naturally jump to the rows and columns that are most constrained, and you will spot placements without consciously going through the elimination process.

To accelerate this, practice with easy puzzles where naked and hidden singles are sufficient. Focus on speed and pattern recognition rather than just getting the answer. Sudoku Royale's Practice mode is ideal for this — unlimited puzzles with no time pressure, so you can build your scanning instincts.

Common Beginner Mistakes

Guessing

The number one mistake beginners make is guessing. When you reach a point where no cell seems solvable, the temptation is to pick a number and hope for the best. Resist this. Valid sudoku puzzles are always solvable through pure logic. If you are stuck, it means you have missed something — not that the puzzle requires guessing.

Guessing leads to cascading errors. You place a wrong number, which leads to more wrong numbers, and eventually you hit a contradiction with no way to tell where the original mistake was. Go back and scan more carefully instead.

Forgetting to Check All Three Constraints

New players sometimes check a number against the row and column but forget the 3x3 box (or vice versa). Always verify all three constraints before placing a number. With practice, this becomes automatic.

Not Using Pencil Marks

As puzzles get harder, keeping track of possibilities in your head becomes impossible. Pencil marks — small candidate numbers written in cells — are essential for intermediate and advanced techniques. Do not think of pencil marks as a crutch; even world-class solvers use them on difficult puzzles.

Starting with Hard Puzzles

Hard puzzles require techniques you have not learned yet. Start with easy puzzles, master the basic techniques, and gradually increase the difficulty. You will know when you are ready — easy puzzles will feel too simple, and you will crave more challenge.

How Sudoku Difficulty Works

Puzzle difficulty is determined not by how many numbers are given, but by which solving techniques are required. Easy puzzles can be solved entirely with naked and hidden singles. Medium puzzles introduce techniques like naked pairs and pointing pairs. Hard puzzles might require X-Wing patterns. And the hardest puzzles demand advanced strategies like Swordfish and XY-Wing.

Do not worry about these advanced techniques now. As a beginner, focus entirely on naked singles, hidden singles, and basic scanning. These three techniques alone will carry you through easy and most medium puzzles. Check out our difficulty levels guide when you are ready to understand the full progression.

Your First Practice Session

Here is a suggested approach for your very first sudoku session:

1. Choose an easy puzzle (one rated "easy" or "beginner").
2. Scan the grid for the most common numbers.
3. Start with the number that appears most often and try to place the remaining instances using cross-hatching.
4. Switch to checking individual cells — look for naked singles in rows, columns, or boxes that are nearly complete.
5. When you place a number, immediately check the surrounding cells to see if that placement reveals anything new.
6. If you get stuck, move to a different area of the grid. Fresh eyes often spot what you missed.
7. Never guess. If nothing is apparent, scan again more carefully.

Your first puzzle might take 20 to 30 minutes, and that is perfectly fine. With practice, easy puzzles will take just a few minutes. Many experienced players solve easy puzzles in under two minutes.

Moving Beyond Beginner

Once you can solve easy puzzles comfortably, you are ready to expand your toolkit. The natural progression is:

1. Master naked and hidden singles (easy puzzles).
2. Learn pencil mark notation and start using it consistently.
3. Study naked pairs and pointing pairs (medium puzzles).
4. Tackle X-Wing and other line-based eliminations (hard puzzles).
5. Explore advanced strategies like XY-Wing and coloring (expert puzzles).

Each new technique opens up a new tier of puzzles. The journey from beginner to advanced solver is genuinely rewarding — there is always something new to learn and a harder puzzle to tackle.

If you want to add a competitive edge to your practice, try speed solving techniques or jump into a real-time match in Sudoku Royale. Competing against other players pushes you to apply techniques faster and builds the kind of pattern recognition that separates good solvers from great ones.

For a quick list of practical advice, check out our 15 tips every beginner should know.