6×6 Sudoku rules
In a 6×6 Sudoku with 2×3 boxes, use the digits 1 through 6 exactly once in every row, every column, and every box. Each box is two rows tall and three columns wide. Keep the given numbers unchanged and use these three constraints to work out the missing numbers.
Classic Sudoku asks you to complete the whole grid. Sudoku Sama, the iPhone and iPad app, uses the same rules but asks you to find one specified digit’s position in a specified row.
What a valid completed grid looks like
| Row / column | C1 | C2 | C3 | C4 | C5 | C6 |
|---|---|---|---|---|---|---|
| R1 | 1 | 2 | 3 | 4 | 5 | 6 |
| R2 | 4 | 5 | 6 | 1 | 2 | 3 |
| R3 | 2 | 3 | 4 | 5 | 6 | 1 |
| R4 | 5 | 6 | 1 | 2 | 3 | 4 |
| R5 | 3 | 4 | 5 | 6 | 1 | 2 |
| R6 | 6 | 1 | 2 | 3 | 4 | 5 |
Read R1 across: 1, 2, 3, 4, 5, 6. Read C1 down: 1, 4, 2, 5, 3, 6. The top-left box contains R1C1–R2C3: 1, 2, 3 and 4, 5, 6. All three groups contain the same six digits, but their order can differ.
Check all three groups
A number belongs in an empty cell only if it does not repeat in that cell’s row, column, or box. Fitting the row alone is not enough: a matching number farther down the column can rule the cell out.
There is no arithmetic requirement. Rows do not need to run in numerical order, and adding their numbers is not a solving method. Unless a puzzle explicitly adds a variant rule, diagonals do not need to contain 1–6.
A useful way to start
- List the digits missing from a row, column, or box before checking cells.
- For one missing digit, scan its possible cells and cross out those blocked by the same digit in a column or box.
- Separate “not ruled out yet” from “proved”: a candidate is not an answer until the constraints force it.
Try the worked one-move example to see an exclusion proof with several empty cells. For the app’s controls and completion goal, read how to play Sudoku Sama.