--- title: "Jigsaw Sudoku Rules: How to Start Solving | Sudoku Flow" description: "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." url: https://sudokuflow.com/guides/jigsaw-sudoku-rules/ language: en last_modified: 2026-11-05 --- [Sudoku guides](https://sudokuflow.com/guides/) # 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 ## Quick answer Jigsaw Sudoku, also called irregular Sudoku, is a 9×9 Sudoku without the usual 3×3 boxes. In their place are nine odd shapes of nine squares each, outlined in bold. Every row, every column and every shape must hold 1 to 9 exactly once. What you know from classic Sudoku still works, with the shapes in place of the boxes. - Rows and columns work as in classic Sudoku. - Nine bold shapes take the place of the 3×3 boxes. - There are no 3×3 boxes, so do not check digits against them. - Start with digits that have one place left in a shape. - The law of leftovers works in any Sudoku, but irregular shapes make it especially useful. ## 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: ```text 3 2 1 9 . . . . . 5 6 8 1 3 . . . 9 . 7 4 8 2 9 5 . 3 . 8 5 . 9 . . . 4 . . 9 . . . . . 7 . 1 2 4 8 6 . . . 2 . . 7 . . . . . . 3 6 2 5 4 9 . . 1 4 . . 6 . 8 9 . ``` Shapes (squares with the same letter form one shape): ```text A A A A B B B C C A A A B B C C C C D A A B B E C C C D D F B B E E E E D D F F F F F E E D D D F F G G G E H H D F G G G I E H H H G G I G I I H H H H I I I I I ``` *Jigsaw Sudoku, Easy, sheet 1: the first 5 moves are marked.* 1. **Row 1, column 4: 9**. 9 has only one place left in its shape. 2. **Row 2, column 1: 5**. 5 has only one place left in its shape. 3. **Row 2, column 3: 8**. 8 has only one place left in its shape. 4. **Row 3, column 2: 7**. 7 has only one place left in its shape. 5. **Row 3, column 5: 2**. 2 has only one place left in its shape. [Printable Jigsaw Sudoku →](https://sudokuflow.com/printables/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. ```text 8 5 . . 6 1 . . 7 . . . 9 . 8 5 . . . . 9 1 . 5 . . . . 8 . . 9 . 3 . 2 . 2 . . 3 . 1 5 . 2 6 3 . . 9 8 7 5 . 1 . 7 . 6 4 . . . . . . 5 . . 8 1 . 9 . . . . . 6 8 ``` Shapes (squares with the same letter form one shape): ```text A A A A A A A B B C C C A A B B B B C D C C C C B B B D D D E E C F F F D E E E E E E E F D D D D F F F F F G G G H H H H H H G G G G H I I I H G G I I I I I I H ``` *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 →](https://sudokuflow.com/printables/jigsaw-sudoku/) [Sudoku variants: Killer, Jigsaw, Diagonal, Samurai and more →](https://sudokuflow.com/encyclopedia/variants/) ## 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 →](https://sudokuflow.com/puzzles/) ## Sudoku guides - [How to Find a Mistake in Sudoku](https://sudokuflow.com/guides/find-a-mistake/) - [7 Common Sudoku Mistakes and How to Avoid Them](https://sudokuflow.com/guides/common-mistakes/) - [Why Won't My Sudoku Solve? A Checklist](https://sudokuflow.com/guides/sudoku-wont-solve/) - [Naked Single vs Hidden Single](https://sudokuflow.com/guides/naked-single-vs-hidden-single/) - [Pointing Pair vs Box/Line Reduction](https://sudokuflow.com/guides/pointing-pair-vs-box-line-reduction/) - [X-Wing vs Swordfish](https://sudokuflow.com/guides/x-wing-vs-swordfish/) - [How to Start a Sudoku: The First Five Minutes](https://sudokuflow.com/guides/how-to-start-sudoku/) - [Stuck on a Hard or Expert Sudoku? The Technique You Need Next](https://sudokuflow.com/guides/stuck-on-hard-sudoku/) - [Sudoku Tips That Actually Work (and Is There a Formula?)](https://sudokuflow.com/guides/sudoku-tips/) - [How to Teach a Child Sudoku: 4×4, Then 6×6, Then 9×9](https://sudokuflow.com/guides/teach-kids-sudoku/) - [Can Every Sudoku Be Solved Without Guessing?](https://sudokuflow.com/guides/solve-without-guessing/) - [Which Sudoku Techniques Do You Actually Need? 60,000 Puzzles Counted](https://sudokuflow.com/guides/sudoku-techniques-you-need/) - [How to Solve Sudoku Faster](https://sudokuflow.com/guides/solve-sudoku-faster/) - [Do the Diagonals Count in Sudoku? 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[App Store iPhone, iPad, Mac](https://apps.apple.com/app/apple-store/id6502922368?pt=125379530&ct=sudokuflow_web&mt=8) [Google Play Android](https://play.google.com/store/apps/details?id=com.rubigogames.sudoku&referrer=utm_source%3Dsudokuflow%26utm_medium%3Dweb%26utm_campaign%3Dsite) Sudoku Flow is made by Rubigo Games, the developer of the Sudoku app recommended on this site.