Sudoku solver
A sudoku solver for any board you are stuck on, from a newspaper, a puzzle book or an app. Type in the numbers, press "Solve", and get the full board, an estimate of the difficulty and a clear answer if something is wrong with the board.
More sudoku
The solver works in two layers. The first solves like a person: it fills cells that have only one possibility and uses pairs, locked candidates and X-wings when it must, which is how the difficulty is set. The second is a computer search that tries every possibility, so it can say for certain whether there is one solution, how many, or none at all.
Frequently asked questions
How do I use the sudoku solver?
Type the numbers from your board into the cells (leave an empty cell empty) and press "Solve". You can also paste the whole board as a line of 81 characters, with 0 or a dot for an empty cell.
What happens if the board has no solution?
The solver says there is no solution. If a number repeats in the same row, column or box, it is marked in red, and it is usually a typing mistake.
Why does it say there is more than one solution?
A valid sudoku has exactly one solution. If numbers are missing from the board (or were typed wrong), there are several ways to fill it. The solver shows one of them and explains that it is not the only one.
Can I get just a hint instead of the whole solution?
"One cell" reveals a single correct number, so you can carry on by yourself.
Explore more: online sudoku, all levels, and very hard sudoku.