--- title: "Can Every Sudoku Be Solved Without Guessing? | Sudoku Flow" description: "We put 10,000 random Sudoku through our app's hint engine: most need no guessing at all, about one in five needs a careful what-if chain, and a few go further." url: https://sudokuflow.com/guides/solve-without-guessing/ language: en last_modified: 2026-11-05 --- [Sudoku guides](https://sudokuflow.com/guides/) # Can Every Sudoku Be Solved Without Guessing? We put 10,000 random Sudoku through our app's hint engine: most need no guessing at all, about one in five needs a careful what-if chain, and a few go further. Updated 2026-11-05 ## Quick answer A proper Sudoku has exactly one answer, so it never needs a lucky guess. But not every puzzle gives way to patterns alone. Of 10,000 random puzzles we put through our app's hint engine, 79.7% were solved with its human techniques, 19.3% needed at least one forcing chain, a careful what if that follows one digit until it breaks, and 1.0% needed something beyond the engine's techniques. - A proper Sudoku has one answer, so a lucky guess is never needed. - 79.7% of random puzzles fall to human techniques alone. - About one in five needs a forcing chain, a systematic what if. - Puzzles in books and apps are chosen and graded, not random. - Every puzzle in our bank of 60,000 is solved without a forcing chain. ## What counts as guessing Guessing means writing in a digit you cannot justify and carrying on, hoping it was right. If it was wrong, you find out many moves later and have to undo everything since. A forcing chain is different: you suppose a digit, follow what must follow, and if that leads to a square with no possible digit, you have proved the supposition wrong. Nothing unproven stays in the grid. Some solvers count that as logic and others as guessing in disguise, so this page keeps the two apart. ## What we measured We made 10,000 random puzzles the way a simple program does: fill a grid at random, then remove clues one by one, in random order, for as long as the puzzle keeps exactly one answer. They start with 22 to 27 clues. Our app's hint engine then solved each one, always taking the easiest step it could find among its techniques. It is the same engine that gives hints in the app and in our solver. ## The result 79.7% of the puzzles were solved with human techniques alone, from singles to almost locked sets; for 32.6% of all puzzles the hardest step was only a hidden single. 19.3% needed at least one forcing chain. The remaining 1.0% (102 puzzles) reached a point where none of the engine's techniques applied: solving them takes a technique beyond the ones it knows, or a longer chain of what ifs. ## Why the puzzles you play are different Puzzles in newspapers, books and apps are not random: they are chosen and graded. Every one of the 60,000 puzzles in our app's bank is solved without a forcing chain. The famous hardest puzzles are the opposite: they were built to need chains, and our page on them shows where our engine has to use one. [The world's hardest Sudoku →](https://sudokuflow.com/data/hardest-sudoku/) ## If you are stuck anyway When you have tried every technique you know, a careful what if is a fair next step. Pick a square with only two possible digits, write one of them in lightly, and follow what it forces. If that leads to a contradiction, the other digit is right. If it does not, you have proved nothing, so rub it out and try the other digit or another square. [Stuck on a Hard or Expert Sudoku? The Technique You Need Next →](https://sudokuflow.com/guides/stuck-on-hard-sudoku/) [Sudoku solver →](https://sudokuflow.com/tools/sudoku-solver/) ## 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/) - [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.