Sudoku Generator & Solver
Play Sudoku online with easy, medium, and hard puzzles. Check solution and get hints.
About this calculator
Generate a new Sudoku puzzle at easy, medium or hard difficulty, play it, check your entries or reveal the solution.
Daily logic practice that is easy to pick up.
How to use it
- Pick the difficulty and press New Puzzle.
- Fill in the grid.
- Press Check; use Solve if you're stuck.
Rules and strategy
Fill the 9×9 grid so each row, each column and each 3×3 box contains the digits 1 to 9 exactly once. Start with cells where only one digit fits (naked singles), then look for digits that fit only one cell in a row, column or box (hidden singles). Pencil-mark candidates, and look for pairs. A well-formed puzzle has exactly one solution.
Worked example
Difficulty
| Easy | Many givens; singles are enough |
| Medium | Needs pairs and pointing |
| Hard | Needs advanced techniques |
Tips and common mistakes
- Scan rows, columns and boxes systematically.
- Write candidates in small numbers.
- Don't guess early.
- Use Check sparingly.
- Practise daily.
Frequently asked questions
What are the rules of Sudoku?
Each row, column and 3×3 box has 1 to 9 once.
Does every puzzle have one solution?
A valid puzzle does.
How do I start?
Look for cells with only one candidate.
Can I get a hint?
Use Check to find mistakes.
Is it free?
Yes.
Is it saved?
No.