Logic GamesLogic & pattern practice
Tango guide
Learn balance, triples, and linked cells.
Puzzle practice guide
How to play Sudoku
Practice Mini Sudoku and larger number grids.
Practice Sudoku online with number grids at different sizes and difficulties, including Mini Sudoku. Each deduction comes from a row, column, or box. Small boards make a useful training ground: there are fewer candidates to track, but the same habits transfer to larger puzzles.
01 / The essentials
Sudoku rules
- Fill every cell with a number allowed by the board size: a six-cell row uses 1 through 6, for example.
- Each number appears exactly once in every row and column.
- Each outlined box also contains every number exactly once. Given numbers cannot be changed.
02 / Build the habit
Sudoku strategy
Find a naked single
For an empty cell, remove numbers already used in its row, column, and box. If only one candidate remains, that number is forced.
Find a hidden single
Pick one missing number and check where it can go within a row, column, or box. A number with only one legal position is forced even when that cell has other candidates.
Use box-line restrictions
If every candidate for a number inside a box lies on one row, that number cannot appear elsewhere along that row. Repeat the same reasoning for columns.
03 / Worked example
Combine three constraints
On a six-number board, a cell’s row is missing 2 and 5. Its column already contains 5. The cell must be 2, provided its box also allows 2. If the box already contains 2, revisit an earlier entry: the cell has no legal candidate.
04 / Put it into practice
A Sudoku practice plan
- Solve a small board by filling singles and checking all three units after each move.
- On a second board, search for hidden singles one number at a time.
- Increase the difficulty when you can distinguish a deduction from a guess. Use candidate notes to avoid repeatedly counting the same possibilities.
A common mistake
Checking only the row and column misses box conflicts. Also, a candidate appearing twice in a unit is not forced; a hidden single needs exactly one legal position.
Do Mini Sudoku and regular Sudoku use the same rules?
They share the rule of one of each number per row, column, and box. The grid size, number range, and box dimensions differ, so use the boundaries drawn on the board.
Guide updated . Rules describe the version on Logic Games.