How to Play Sudoku: Rules, Tips and Strategies for Beginners
Sudoku looks intimidating at first — a 9×9 grid full of little squares and a scattering of numbers. But the rules fit in a single sentence, and the first puzzle you finish will feel like a small triumph. Here's everything you need to know to play, from the basics to your first real strategies.
The one rule of sudoku
A sudoku grid is divided into nine boxes (3×3 blocks), and each box is divided into nine cells. Some cells already contain numbers — those are your clues. Your job is to fill the empty cells so that every row, every column and every box contains the numbers 1 to 9 exactly once.
That's it. Three constraints, one rule:
- Each row has the numbers 1–9, none repeated.
- Each column has the numbers 1–9, none repeated.
- Each box has the numbers 1–9, none repeated.
No math is involved — sudoku is pure logic. You never add, subtract or guess; you simply look at what's missing and where it can possibly go.
What makes a puzzle fair
A well-made sudoku has exactly one solution. That means every correct puzzle can be solved by logic alone — there is always at least one cell whose number you can pin down with certainty, and if you keep finding them, you'll never need to guess. If you ever feel forced to guess, you've missed a deduction somewhere.
Every puzzle from our free sudoku generator is checked for a single unique solution before it's shown to you, so you can trust that it's always solvable — and always fair.
Getting started: your first moves
Begin with the easiest thing to find: a nearly complete row, column or box. If a box already has eight of its nine numbers, the missing number is the only one not present. Write it in.
Then use the crossing rule:
- Pick a box and list the numbers that are missing from it.
- For each missing number, look at the row and column that pass through its empty cells.
- If a missing number already appears in one of those rows or columns, that cell is ruled out.
- If only one empty cell in the box remains possible for that number, that's where it goes.
This technique — scanning a box and eliminating options with its crossing rows and columns — is called cross-hatching, and it solves most easy and medium puzzles by itself.
Three strategies that take you further
- Scanning (cross-hatching): the box-by-box elimination described above. Do it for every box, then every row and column, and repeat — each number you place opens up new eliminations.
- Only option (naked single): a cell whose row, column and box already contain eight of the nine numbers has only one possible value. Fill it in.
- Pencil marks: on paper, jot the candidate numbers in each cell's corner. When a candidate is eliminated, cross it off. When a cell has just one candidate left, that's its number.
Common mistakes to avoid
- Guessing. If you guess, you'll often paint yourself into a corner. Look for the certain move instead.
- Repeating a number in a box. Check the box, not just the row and column, before you write anything down.
- Skipping the easy stuff. Beginners rush past the single-move cells that unlock the rest of the puzzle.
Smaller grids: sudoku for kids and beginners
The same rule works on any grid size. Our sudoku puzzle maker offers three sizes:
- 4 × 4 Mini — numbers 1–4 in 2×2 boxes. A great first puzzle for young children.
- 6 × 6 Junior — numbers 1–6 in 2×3 boxes. A gentle step up.
- 9 × 9 Classic — the traditional grid, at easy, medium or hard levels.
Every size can be solved on screen with our built-in checker, or printed blank to solve on paper — with the answers available whenever you need them.
Ready to play?
Open the sudoku generator, pick a size and difficulty, and a fresh puzzle appears instantly. If you're just starting, try the 6×6 or an easy 9×9 and apply cross-hatching until it clicks — most people solve their first puzzle in under ten minutes.