How to Play Sudoku Step by Step: Complete Beginner's Guide
Sudoku a Day Blog ·
Sudoku looks intimidating the first time you see it. A 9×9 grid, dozens of blank cells, and numbers scattered around that seem to follow no obvious pattern. But here is the thing: Sudoku requires no math. It is a logic puzzle, and the rules fit in two sentences. Once you understand them, the rest is practice.
This guide walks you through how to play sudoku for beginners — step by step, from blank grid to your first solution. If you want an interactive version, follow along with our how-to-play guide that lets you try each technique live.
The Three Rules of Sudoku
Every Sudoku puzzle — easy or expert — follows exactly three rules:
- Each row must contain the digits 1 through 9, with no repeats.
- Each column must contain the digits 1 through 9, with no repeats.
- Each 3×3 box must contain the digits 1 through 9, with no repeats.
That is it. The grid starts with some numbers pre-filled (called "givens"). Your job is to fill in the rest so every row, column, and box is complete without any digit appearing twice.
You do not add, subtract, or calculate anything. The digits are just symbols — you could use letters A through I and the puzzle would work identically.
Step 1: Understand the Grid
The 9×9 grid is divided into nine 3×3 boxes. Each box, each row, and each column is called a "unit." A solved puzzle has every unit containing exactly the digits 1 through 9.
Before you place any number, take 30 seconds to scan the given clues. Notice which digits appear frequently and which appear rarely. Heavily represented digits are often the easiest to place first.
Step 2: Start With Nearly Complete Units
Look for any row, column, or box that already has eight digits filled in. If a row has eight numbers and one empty cell, the missing digit is the one not yet in that row. Fill it in immediately — this is the easiest move in Sudoku.
Most beginner puzzles give you several of these at the start. Work through all of them before trying anything more complex.
Step 3: Scan Digit by Digit
Pick one digit — say, 7 — and look at where all the 7s already appear on the grid. In any row, column, or box that already contains a 7, no other cell in that unit can hold a 7. Use this information to eliminate possibilities.
Work through the grid looking for cells where your chosen digit is the only option left in its row, column, and box. When you find one, place it.
This technique — called scanning — is the foundation of all Sudoku solving. Repeat it for every digit, 1 through 9.
Step 4: Use Elimination (Naked Singles)
When scanning a digit doesn't immediately give you a placement, try working from the cell's perspective. For each empty cell, ask: which digits are already used in this cell's row, column, and box?
If only one digit remains as a possibility, place it. This is called a naked single — one of the most common moves in easy and medium Sudoku.
Example: a cell sits in row 3 (which already has 1, 2, 4, 5, 6, 8, 9), column 5 (which has a 3), and its 3×3 box (which has a 7). The only digit not covered is 3 — but 3 is already in its column. That leaves nothing. This means you have an error somewhere else. But if only one digit is uncovered, place it.
Step 5: Use Pencil Marks for Harder Cells
When you cannot immediately determine a cell's digit, write small candidate numbers in the corner of the cell — one for each digit that is still possible. These are called pencil marks or candidate marks.
As you fill in cells elsewhere, return to your pencil-marked cells and cross out newly impossible candidates. When a cell's candidates reduce to one, you have your answer.
On paper, use a pencil. In a Sudoku app, there is usually a "notes" mode. Either way, pencil marks are how you manage complexity without guessing.
Step 6: Check Your Work and Repeat
After each placement, scan nearby units. A newly placed digit often creates new naked singles in adjacent rows, columns, or boxes. Easy puzzles are designed so that solving one cell reveals the next in a chain. Work through the chain before scanning globally again.
If the chain runs out, scan all digits again. Easy puzzles are fully solvable by scanning and naked singles alone.
What Comes After Easy Puzzles?
Once easy puzzles feel routine — typically after five to ten completions — you are ready to step up. Medium puzzles introduce situations where scanning and naked singles alone don't resolve every cell. You will need techniques like locked candidates, naked pairs, and hidden pairs.
Do not rush this progression. Accuracy at easy builds the pattern recognition that makes medium more tractable. For a full progression path, visit our complete beginner guide which covers the route from easy to expert.
Practice With Printables
One of the most effective ways to build speed and accuracy is to work through grids on paper. Pencil-and-paper solving forces you to think through moves before committing, which trains better habits than digital solving where you can undo instantly.
Download and print a set from our collection of free printable sudoku puzzles — easy packs come in single-page formats designed for beginners.
Frequently Asked Questions
Do I need to be good at math to play Sudoku?
No. Sudoku uses only the digits 1 through 9 as symbols — you never add, subtract, or calculate anything. It is a logic puzzle, not a math puzzle. Anyone who can count to 9 can learn to play.
How long does it take to learn Sudoku?
Most beginners complete their first easy puzzle within 20–40 minutes after reading the rules. The core technique — scanning and elimination — takes about five minutes to understand and one or two puzzles to internalize.
What is the best way to start solving a Sudoku puzzle?
Start by scanning for rows, columns, or boxes that are nearly complete. Then scan digit by digit — pick a number and look at where it already appears to narrow down where it can go in empty cells. This approach solves most easy and many medium puzzles without any guessing.
Should I guess when I get stuck?
Not as a first step. Every properly constructed Sudoku has exactly one solution reachable by logic. When you feel stuck, try a different area of the grid or use pencil marks to track possibilities. Guessing often creates errors that are hard to trace.
What is the difference between easy and hard Sudoku?
Easy puzzles are solvable with scanning and naked singles alone. Medium puzzles may require locked candidates or naked pairs. Hard and expert puzzles need more advanced techniques. The number of given clues is also lower in harder puzzles, leaving more cells empty at the start.