How to Solve Samurai Sudoku: Where to Start

Samurai Sudoku is five 9×9 grids that share corner boxes. The rules, why the shared boxes are the place to start, and the first moves on a real puzzle.

Updated 2026-11-06

The rules

A Samurai Sudoku has five 9×9 grids. The middle grid shares one 3×3 box with each corner grid: its top-left box is also the bottom-right box of the top-left grid, and so on around its four corners. Fill all five so that every row, column and box of each grid holds the digits 1 to 9 exactly once. Five grids of 81 squares, less the four shared boxes counted twice, make 369 squares.

Rows stop at the edge of their grid

Where the grids meet, a line of squares runs right across the sheet: 21 squares through three grids. It is not one long row. It is a row of one corner grid, a row of the middle grid and a row of the other corner grid, overlapping in the shared boxes. Nine digits cannot fill 21 squares without repeats, so check a digit only against the rows of the grids its square belongs to. The same goes for columns.

Where to start: the shared boxes

A square in a shared box belongs to two grids at once. Its box is the same in both, but it has a row and a column in each grid, so the digits in two rows and two columns rule numbers out of it, not just one row and one column. That often makes these squares the first to fill.

On our 200 printable Samurai sheets, 12.0% of the empty squares in shared boxes can be filled straight away with a single (a digit with one place left in a row, column or box, or a square with one digit left), against 7.9% of the other empty squares. And every digit you place there counts in two grids.

The first moves on a real puzzle

This is the first Easy sheet from our printable Samurai Sudoku, with the shared boxes shaded. The 5 marked squares are the first moves we found by looking in the shared boxes first, in this order:

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Samurai Sudoku, Easy, sheet 1: the shared boxes are shaded and the first 5 moves are marked.

Top-left grid, row 8, column 7: 7. 7 has only one place left in this box.
Top-left grid, row 8, column 9: 3. 3 has only one place left in this box.
Top-right grid, row 7, column 2: 7. 7 has only one place left in this box.
Top-right grid, row 9, column 3: 9. 9 has only one place left in this box.
Bottom-right grid, row 2, column 2: 6. 6 has only one place left in this box.

Printable Samurai Sudoku →

Tips

Treat each grid as a classic Sudoku, and come back to the shared boxes whenever you place a digit near them.
When a digit goes into a shared box, look at both grids: it may give the next move in either.
If one grid stalls, move on to another. A shared box filled from the other side often gets it going again.
Pencil marks help on a sheet this big. Start them in the shared boxes, where two grids narrow the choices.
Our printable Samurai sheets need only singles, so there is always a next move without guessing.

Printable Samurai Sudoku →Sudoku variants: Killer, Jigsaw, Diagonal, Samurai and more →

Practice

Every Find the Mistake puzzle on this site has exactly one wrong digit, and you can play each board right on its page.

Play the puzzles →