--- title: "How to Make a Sudoku Puzzle, Step by Step | Sudoku Flow" description: "How a Sudoku is made: start from a finished grid, take digits out while it keeps exactly one answer, then grade it. By hand, and how our app does it." url: https://sudokuflow.com/guides/how-to-make-a-sudoku/ language: en last_modified: 2026-11-06 --- [Sudoku guides](https://sudokuflow.com/guides/) # How to Make a Sudoku Puzzle, by Hand or by Program How a Sudoku is made: start from a finished grid, take digits out while it keeps exactly one answer, then grade it. By hand, and how our app does it. Updated 2026-11-06 ## Quick answer The usual way to make a Sudoku is backwards. Start from a finished grid, then take digits out one at a time, putting a digit back whenever the puzzle would get a second answer. Stop when no more can come out, or earlier for an easier puzzle. Last, solve it the way a person would to see how hard it is. Our app's puzzles were made this way, by a program. - Start from a finished grid, not an empty one. - Take digits out one by one, and put one back if a second answer appears. - A puzzle's level depends on the hardest step it needs, not only on how many digits are left. - Starting from the answer of our first Easy puzzle, our program took 57 digits out for good; the other 24 had to stay. - Our free Sudoku maker makes and checks puzzles for you. ## Step 1: a finished grid You need a correct, completely filled grid. A quick way by hand: write 1 to 9 in the top row, start each next row three places further along, and start each new band of three rows one place further. Every row, column and box then holds 1 to 9 once. A grid made like this has an obvious pattern. Swapping digits throughout (every 1 for a 5, say), swapping rows inside a band, swapping whole bands, and doing the same with columns all keep it a finished Sudoku while hiding the pattern. ```text 1 2 3 | 4 5 6 | 7 8 9 4 5 6 | 7 8 9 | 1 2 3 7 8 9 | 1 2 3 | 4 5 6 ------+-------+------ 2 3 4 | 5 6 7 | 8 9 1 5 6 7 | 8 9 1 | 2 3 4 8 9 1 | 2 3 4 | 5 6 7 ------+-------+------ 3 4 5 | 6 7 8 | 9 1 2 6 7 8 | 9 1 2 | 3 4 5 9 1 2 | 3 4 5 | 6 7 8 ``` *A finished grid made by hand: each row is the one above it, shifted.* ## Step 2: take digits out Take out one digit at a time, in any order. After each one, check that the puzzle still has exactly one answer. If it now has two, put the digit back and try another square. When no digit can come out any more, the puzzle has as few givens as that grid and that order allow. ## Step 3: make sure there is one answer This is the hard part by hand: you must be sure that no other way of filling the grid works. Solving the puzzle yourself step by step, without guessing, is a good test. If every step is forced, nothing else can fit, so the answer is unique. A program can simply count the answers. [Can a Sudoku Have Two Solutions? →](https://sudokuflow.com/guides/can-sudoku-have-two-solutions/) ## A real puzzle made this way We did it with a program, starting from the answer of the first Easy puzzle on our printable sheets. It tried each of the 81 squares once, in a random order: 57 digits came out for good, and 24 had to go back because a second answer appeared. Those 24 digits make a puzzle with exactly one answer. Its hardest step is a Pointing Pair, so our app would file it under Hard: ```text . 6 . | . . . | 8 . . 9 . . | 2 5 3 | . . . . . 5 | . . . | 3 . 7 ------+-------+------ 6 . . | . . 5 | 1 8 2 . . . | . . 1 | . . . . 5 . | . . . | 4 . . ------+-------+------ . 4 3 | 1 . . | . . . . 1 . | . . . | . . 4 . . . | 7 . 6 | . . . ``` *A puzzle made from a finished grid: 24 digits left and exactly one answer.* ## How our app's puzzles were made The same way, by a program. It fills a random finished grid, keeps one random square in each box, then tries taking out the other squares in a random order, putting a digit back whenever a second answer appears, until the puzzle has as many empty squares as its level calls for; when a grid cannot get there, it starts again aiming for two fewer. Our hint engine then solves every puzzle step by step and files it under the hardest technique it needed. Easy puzzles had some digits given back afterwards, to make them gentler, and were checked again. [What each Sudoku difficulty level asks of you →](https://sudokuflow.com/data/sudoku-difficulty-levels/) [How computers solve Sudoku →](https://sudokuflow.com/encyclopedia/computers/) ## Tips for making your own - Stop early for an easier puzzle: more givens usually mean easier steps. - Many puzzle makers place the givens in a symmetric pattern. It looks good, but it is a tradition, not a rule. - Test-solve your puzzle, or ask someone else to, before you share it. - Our Sudoku maker makes new puzzles in your browser, checks that each has exactly one answer and rates it with our app's hint engine. [Sudoku maker →](https://sudokuflow.com/tools/sudoku-maker/) ## 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? Diagonal Sudoku (Sudoku X) Rules](https://sudokuflow.com/guides/diagonal-sudoku-rules/) - [How to Solve Killer Sudoku: Where to Start](https://sudokuflow.com/guides/how-to-solve-killer-sudoku/) - [Jigsaw Sudoku Rules and How to Start](https://sudokuflow.com/guides/jigsaw-sudoku-rules/) - [6×6 Sudoku: Rules and Tips for Beginners](https://sudokuflow.com/guides/6x6-sudoku-rules/) - [How to Solve Samurai Sudoku: Where to Start](https://sudokuflow.com/guides/how-to-solve-samurai-sudoku/) - [Is Sudoku Math? Logic, Not Arithmetic](https://sudokuflow.com/guides/is-sudoku-math/) - [Why Medium Sudoku Suddenly Feels Harder](https://sudokuflow.com/guides/why-is-medium-sudoku-harder/) - [Can a Sudoku Have Two Solutions?](https://sudokuflow.com/guides/can-sudoku-have-two-solutions/) - [How Long Does a Sudoku Take? Times by Level](https://sudokuflow.com/guides/how-long-does-sudoku-take/) - [16×16 Sudoku: Rules and How to Start](https://sudokuflow.com/guides/16x16-sudoku-rules/) - [Sudoku Notes: When and How to Use Pencil Marks](https://sudokuflow.com/guides/sudoku-notes-pencil-marks/) - [Sudoku for Seniors: Large Print Puzzles and How to Start](https://sudokuflow.com/guides/large-print-sudoku-for-seniors/) - [Wordoku: Sudoku with Letters Instead of Numbers](https://sudokuflow.com/guides/wordoku-letter-sudoku/) - [What each Sudoku difficulty level asks of you](https://sudokuflow.com/data/sudoku-difficulty-levels/) - [Sudoku facts](https://sudokuflow.com/guides/sudoku-facts/) - [Sudoku checker](https://sudokuflow.com/tools/sudoku-checker/) - [Sudoku for kids](https://sudokuflow.com/printables/kids/) - [Find the Mistake Sudoku](https://sudokuflow.com/find-the-mistake/) ![Sudoku app icon](https://sudokuflow.com/assets/app-icon.png) ## Want more boards like this? We also make a Sudoku app for iPhone, iPad, Mac and Android. There are no ads in it at all, it works offline, and when you ask for a hint it shows you the technique instead of just filling in a number. [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.