Sudoku Solver
Solve any Sudoku puzzle
About this calculator
The Sudoku Solver fills any 9×9 Sudoku puzzle so every row, column and 3×3 box contains the digits 1–9 exactly once. Enter your clues on the interactive grid and it finds the solution instantly using backtracking search with the minimum-remaining-values heuristic. It checks that the clues are legal, tells you whether the puzzle has a single unique solution, and colour-codes each answer by whether it was deduced by pure logic or required a search.
How to use the Sudoku Solver calculator
- Enter the values for your problem into the input fields.
- Read the result — it updates instantly as you type.
- Check the formula and the visual explanation to follow how the answer was found.
- Copy the page URL to share the exact calculation.
Common examples
- A classic 30-clue newspaper puzzle → solved by pure logic (naked and hidden singles), unique solution
- A 21-clue expert puzzle → solved with MRV backtracking search, still verified unique
- An empty grid → reported as having 2+ solutions, so not a proper puzzle
- Two 5s in the same row → the conflicting cells are flagged as invalid givens
Frequently asked questions
How does the Sudoku Solver calculator work?
Enter your values and the calculator applies the exact mathematical method for this problem, showing the result together with the formula it used. Everything is computed with high-precision arithmetic, so the answer you see is not limited by ordinary floating-point rounding.
When would I use the Sudoku Solver calculator?
It is useful for homework and exam preparation, for checking work done by hand, and whenever a step in a larger problem needs this calculation done quickly and reliably.
How accurate are the results?
Calculations run at 30 significant digits of precision internally. Displayed values are rounded for readability, but the underlying result is far more precise than a typical hand or pocket-calculator computation.
Can I share a specific calculation with someone else?
Yes. Every value you enter updates the URL, so copying the address bar and sharing the link reopens the exact same calculation for whoever clicks it.