Jigsaw Sudoku Rules and How to Start

Jigsaw Sudoku, also called irregular Sudoku, swaps the 3×3 boxes for nine odd shapes. The rules, the first moves on a real puzzle and the law of leftovers.

Updated 2026-11-05

The rules

A Jigsaw Sudoku is a 9×9 grid divided into nine shapes of nine squares each. Fill it so that every row, every column and every shape holds each digit from 1 to 9 exactly once. As in classic Sudoku, a good puzzle has exactly one answer.

What changes from classic Sudoku

Only the boxes change. Habit is the main trap: the eye keeps looking for 3×3 boxes that are not there. A digit may appear twice in the same 3×3 area of the grid as long as it does not repeat in a row, a column or a shape. And because a shape can wind across several rows and columns, one digit in it can rule out squares that are far apart.

The first moves on a real puzzle

This is the first Easy sheet from our printable Jigsaw Sudoku, with 36 digits given. The 5 marked squares are the first moves a beginner would find, in this order:

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Jigsaw Sudoku, Easy, sheet 1: the first 5 moves are marked.

Row 1, column 4: 9. 9 has only one place left in its shape.
Row 2, column 1: 5. 5 has only one place left in its shape.
Row 2, column 3: 8. 8 has only one place left in its shape.
Row 3, column 2: 7. 7 has only one place left in its shape.
Row 3, column 5: 2. 2 has only one place left in its shape.

Printable Jigsaw Sudoku →

The law of leftovers

Take some whole rows and the same number of shapes that together nearly fill them: two rows and two shapes, or three rows and three shapes. Every digit appears once in each row and once in each shape, so the squares of the rows that the shapes leave out hold exactly the same digits as the squares of the shapes that stick out of the rows. The same works with columns.

In the puzzle below (Easy, sheet 52), rows 1 to 3 and the 3 shapes that nearly fill them leave one square on each side: row 3, column 2 inside the rows and row 4, column 6 outside them. So those two squares hold the same digit, in this puzzle 7. Whatever you find out about one of them, you also know about the other.

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Jigsaw Sudoku, Easy, sheet 52: rows 1 to 3 and their 3 shapes leave the two shaded squares, which hold the same digit.

Tips

Look at small, compact shapes first: they behave much like boxes.
Long, thin shapes cross many rows or columns, so each digit placed in them rules out a lot.
A shape that lies almost entirely in a few rows or columns is a hint that the law of leftovers will help.
Check a new digit against its shape, not against the 3×3 area around it.

Printable Jigsaw 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 →