How to Play Sudoku
Sudoku is a number placing puzzle on a nine by nine grid. You never add anything up and you never guess. Every answer is already decided by the numbers in front of you, and your job is to work out which one it has to be.
A puzzle starts with some squares filled in. Those givens are all you need. Fill the rest so that every row, every column and every three by three box holds the numbers 1 to 9 exactly once.
Play SudokuHow to play Sudoku
- Pick an empty square and ask which numbers are still allowed there. Anything already in its row, its column or its box is out.
- If only one number survives, write it in. That is a naked single and it is the bread and butter of easy puzzles.
- Look at it the other way too. If a number can only go in one square of a row, column or box, it goes there even if that square had other candidates.
- Use pencil marks for squares with two or three options, then watch those options vanish as the grid fills in.
- Keep going until the grid is complete. There is exactly one solution, so if two numbers both seem to fit, one of your earlier entries is wrong.
The rules in short
- Each row holds 1 to 9 with no repeats.
- Each column holds 1 to 9 with no repeats.
- Each three by three box holds 1 to 9 with no repeats.
- The givens never change, and every puzzle has one answer.
Tips that make a real difference
Scan by number rather than by square. Take the sevens, look at every box that still needs one, and see which boxes have only one legal home for it. This finds far more than staring at a single empty cell.
When you are stuck, hunt for pairs. Two squares in the same unit that can only hold the same two numbers lock those numbers away from every other square in that unit, which usually breaks the deadlock.
Write in pencil marks only once scanning dries up. Filling in every candidate too early turns the grid into noise.
Frequently asked questions
Is Sudoku maths?
No. The symbols could be nine colours or nine letters and nothing would change. It is pure logic about where things can and cannot go.
Does a Sudoku puzzle always have one answer?
A proper one does, and every puzzle here is checked for that before it reaches you. If you can find two different completed grids, the puzzle was faulty.
Should I ever guess?
You never need to. Every puzzle here can be finished by reasoning alone, so a guess usually means there is a deduction nearby you have not spotted yet.
Is there a new puzzle every day?
Yes. Each day has its own puzzle on every difficulty, and you can go back to any earlier day from the previous games button.