Sudoku Game

How to play Sudoku

Sudoku is a logic puzzle played on a square grid split into smaller boxes. Some numbers are filled in to start, and your job is to fill every empty square so that each row, each column and each box holds every number once, with no number repeated in any row, column or box. On the classic 9 by 9 grid that means the numbers 1 to 9; on the smaller kid grids it means 1 to 4 or 1 to 6. You never need to guess. Every puzzle here has exactly one solution you can reach with logic alone.

To play, tap a square and type the number. On a phone or tablet the number keypad opens by itself, and on a computer you can also move around the grid with the arrow keys. Turn on Notes to pencil in the small maybe numbers when you are not sure yet, which is how experienced solvers keep track of their thinking. Use Hint if you get truly stuck, and Erase to clear a square. The game checks each entry against the solution and counts mistakes, so you always know where you stand.

Which grid size should a child start on

The 4 by 4 grid is the right first Sudoku for most children around five or six. It uses only the numbers 1 to 4 and has four small boxes, so a child can see the whole puzzle at once and finish it in a minute or two, which is exactly the quick win that makes them want another. The 6 by 6 grid, with numbers 1 to 6, is the natural next step for roughly ages seven and up. The classic 9 by 9 is where most people picture Sudoku, and a child who is comfortable with 6 by 6 on Easy is usually ready to try it. There is no rush to the big grid; the thinking is the same at every size, whether on screen or on a printable Sudoku sheet for the car or the classroom.

How to get better at Sudoku, one real technique at a time

There is no trick that solves a Sudoku for you, but there are a handful of genuine techniques that turn a stuck grid into an easy one. They build on each other, so learn them in order.

Start by hunting for the almost-full lines. A row, column or box with just one empty square can only take the one number it is missing, so fill those first. Each number you place often makes a neighbor almost-full too, and the grid starts to unzip.

Next, learn to scan a single number across the grid. Pick a number, say 5, and look at the boxes that still need one. A box cannot use a 5 in any row or column that already has a 5 somewhere else, so cross those squares off in your head. Often only one square in the box survives, and that is where the 5 goes. Solvers call this cross-hatching, and it is the single most useful habit to build.

When scanning runs dry, switch on Notes and pencil the possible numbers into each empty square. Now you are looking for two patterns. A naked single is a square where your notes show only one number left, so that number must go there. A hidden single is a number that appears in your notes for only one square in a whole row, column or box, even if that square has other notes too; it has nowhere else to live, so place it.

The last technique for harder grids is the pair. If two squares in the same row, column or box both show the exact same two candidates and nothing else, then those two numbers are locked into those two squares. You do not yet know which goes where, but you can safely erase both numbers from the notes of every other square in that line, and that usually reveals a fresh single somewhere nearby.

That is the honest whole of it. Almost every puzzle up to Hard falls to scanning and singles alone, and pairs handle most of the rest. Work in small steps, trust the logic, and never guess.

The calm focus Sudoku asks for

Sudoku is a calm, screen-friendly way to practice focus, patience and logical thinking. It suits a wide range of ages, works well as a quiet activity at home, and makes a good settle-down task in the classroom. There is no clock pressure unless you want it, so it is as relaxing or as challenging as you choose.

Frequently asked questions