Sudoku for Kids (4x4)
Four rows, four columns, four little boxes of four cells, and the digits 1 to 4. Each digit appears once in every row, once in every column and once in every box. The pad under the grid has four buttons on it, and a typical board here leaves four or five digits filled in to start with. A kids sudoku on this site means exactly that and nothing more: four digits, four boxes, and never a step that needs one cell compared against another.
Only 288 finished grids exist
The complete four-by-four grid – the shape usually written 4×4 – can be filled in 288 legal ways, and that is the entire universe of this puzzle. Fix the top row as 1 2 3 4 and just twelve arrangements remain; every other finished grid is one of those twelve with the four symbols renamed, and there are 24 ways to rename four symbols. It is a rare case of a puzzle whose whole space can be written out on a couple of pages, and it is worth mentioning to an older child – the grid in front of them is one of 288 things, and they are working out which.
Seven neighbours, and a child can see all of them
Every cell shares a unit with seven others: three along its row, three down its column, and one more in its box that is in neither. That is the whole constraint. A four-year-old cannot track the twenty peers of a full-size grid, but seven is within reach of a glance. That is the real argument for a sudoku for kids being four-by-four rather than a nine-by-nine with extra digits filled in, and it is also why the size stops being a challenge fairly quickly.
The sentence to say out loud
Ask which number is missing from this row. That is a counting question rather than a logic question, a child who can count to four can answer it, and it is exactly the deduction the puzzle is made of. When a row has one gap the answer is immediate; when it has two, ask the same question of the column crossing one of the gaps. Every board on this page is graded so that a question of that shape always has an answer available somewhere on the grid – no board here ever needs comparing one cell against another.
What the board does when a digit is wrong
A digit that repeats in a row, a column or a box turns red the moment it is entered, which gives an immediate and undramatic signal without saying what the right answer was. Check gives a count of how many filled cells disagree with the solution, which is more use to the adult than to the child. Hint fills in one cell that can be worked out from what is already there. A clock runs above the grid and nothing whatever depends on it – it can be ignored completely, and with a small child it probably should be.
When four-by-four stops being enough
The usual sign is that the grid is being filled in without pauses. The next step is not a nine-by-nine grid, which is a big jump in both size and technique, but the six-by-six: six digits, rectangular boxes, and enough room that a wrong guess is no longer obvious straight away. From there the full-size easy grid uses the same single deduction, just fifty-odd times over.