Sudoku looks intimidating the first time you see a grid full of empty boxes — but the rules are simple, and once they click, Sudoku becomes one of the most satisfying logic puzzles you can play. This guide walks you through exactly how to play Sudoku, step by step, plus the core strategies every beginner needs to start solving puzzles with confidence.
What Is Sudoku?
Sudoku is a number-placement puzzle played on a 9×9 grid, divided into nine smaller 3×3 boxes. The grid starts partially filled with numbers, called “givens” or “clues.” Your job is to fill in every empty cell using the numbers 1 through 9, following three simple rules.
The Rules of Sudoku
There are only three rules to remember:
- Each row (left to right) must contain the numbers 1 through 9, with no repeats.
- Each column (top to bottom) must contain the numbers 1 through 9, with no repeats.
- Each 3×3 box must contain the numbers 1 through 9, with no repeats.
That’s it. Every number from 1 to 9 appears exactly once in every row, every column, and every 3×3 box. When all 81 cells are filled without breaking any of these rules, the puzzle is solved.
How to Play Sudoku: Step-by-Step
1. Study the Grid Before You Start
Before placing a single number, scan the whole board. Notice which rows, columns, and boxes already have several numbers filled in — these are the easiest places to find your first moves, since there’s less room for a number to hide.
2. Look for the “Only One Spot Left” Cells
The simplest solving technique is scanning for cells where only one number can possibly fit. If a row, column, and box intersecting at a cell already rule out eight of the nine numbers, the ninth is your answer.
3. Use Elimination Within Rows, Columns, and Boxes
Pick a number, say 5, and look at where it already appears across the grid. Any row, column, or box that already contains a 5 can’t have another one. Cross those areas off mentally (or with pencil marks — more on that below) and see where 5 is still allowed to go within a given box.
4. Take Pencil Notes on Harder Puzzles
As puzzles get more difficult, you won’t always find a cell with only one possible answer right away. That’s where pencil marks (or “notes”) come in — small numbers jotted in the corner of a cell to track every number that could still fit there. As you fill in more of the grid, you can eliminate candidates from your notes until only one possibility remains.
On Play Sudoku, you can toggle Notes mode on to place multiple candidate numbers in a single cell, then clear them as you narrow things down.
5. Work the Easy Numbers First
Some players like to work through the grid one number at a time — find every place a 1 can go, then every place a 2 can go, and so on. Others prefer to work cell by cell. Both approaches work; try each and see which feels more natural to you.
6. Double-Check Before Locking In a Number
A wrong placement early in the puzzle can cascade into a much bigger mess later on. If you’re not fully certain, it’s often faster to leave a cell as pencil marks a little longer than to guess and have to backtrack.
Beginner Strategies That Actually Work
Once you’re comfortable with the basic rules, these techniques will speed up your solving:
- Scanning: Systematically checking rows and columns for where a specific number is missing from a box.
- Cross-hatching: Combining row and column scanning at the same time to narrow down a number’s possible position within a box to just one or two cells.
- Naked pairs: When two cells in the same row, column, or box can only contain the same two candidate numbers, those two numbers can be eliminated from every other cell in that row, column, or box.
- Process of elimination: Working backward from what’s not possible, rather than only forward from what is.
Start with easier puzzles to build these habits before jumping into expert-level grids — the same logic applies at every difficulty, but harder puzzles require chaining more of these techniques together.
Common Beginner Mistakes to Avoid
- Guessing instead of deducing. Sudoku is a logic puzzle, not a guessing game — every correctly designed puzzle can be solved through pure deduction, without ever needing to guess.
- Ignoring the 3×3 boxes. New players often focus only on rows and columns and forget to check the box constraint, which is just as important.
- Not using notes on harder puzzles. Trying to hold every candidate number in your head works for easy puzzles but quickly breaks down on medium and hard grids.
Frequently Asked Questions
Is Sudoku good for your brain?
Sudoku is widely used as a mental exercise for pattern recognition, logical reasoning, and concentration. Many players use it as a daily habit similar to a crossword.
How long does it take to solve a Sudoku puzzle?
It depends on difficulty and experience. Beginner puzzles might take 5–10 minutes, while expert-level puzzles can take 30 minutes or longer, even for experienced solvers.
Do I need math skills to play Sudoku?
No. Despite using numbers 1–9, Sudoku involves no arithmetic at all — it’s purely a logic and pattern-matching puzzle. The numbers could just as easily be letters or symbols.
What’s the difference between Sudoku difficulty levels?
Easier puzzles start with more filled-in numbers and require fewer advanced techniques to solve. Harder puzzles start with fewer clues and often require combining multiple strategies, like naked pairs or cross-hatching, to make progress.
Ready to Practice?
Now that you know the rules and the core strategies, the best way to improve is simply to play. Start a free Sudoku puzzle on Play Sudoku and pick a difficulty level that matches where you’re at — every puzzle is generated fresh, so you’ll never run out of new challenges to sharpen your skills on.
In this short video we will explain how to play Sudoku.