All Sudoku Variants
4×4 · Size Variant

Sudoku 4×4

Also known as Shidoku, Kids Sudoku

A 4×4 grid with 2×2 boxes and digits 1–4 — the gentlest introduction, popular with children and beginners.

1 2 3 4

An example 4×4 Sudoku: digits 1–4 fill every row, column and 2×2 box.

4×4 Sudoku is the smallest Sudoku there is: a four-by-four grid using only the digits 1–4, split into four 2×2 boxes. Each row, column and box holds 1, 2, 3 and 4 exactly once. With just sixteen cells it can be solved in under a minute, which makes it the ideal first puzzle for young children and an instant demonstration of how Sudoku works.

The rule: 1–4 in every row, column and 2×2 box

The rules are Classic Sudoku in miniature. Fill the grid so no digit repeats in any row, any column or any of the four 2×2 boxes. Here is a completed 4×4 grid — notice how each of the four small boxes contains 1, 2, 3 and 4.

1 2 3 4 3 4 1 2 2 1 4 3 4 3 2 1

A finished 4×4 grid: every row, column and 2×2 box holds 1–4 once.

The simplest Sudoku of all

Because there are only four digits and four cells per unit, a 4×4 almost solves itself: once a row or box has three of its four digits, the last is forced. Most 4×4 puzzles need only two or three given digits to have a single answer, and the whole solve is a chain of "only one option left" deductions — the purest possible introduction to the logic behind every larger grid.

A perfect teaching tool

The 4×4 is where scanning is learned. A child can look along a row, see that a 3 is missing, and find the one cell in the box where it fits — the exact habit that, scaled up, solves a 9×9 or a 16×16. Because success comes quickly, it builds confidence before the grids grow. From here the natural next step is the 6×6 grid, then the full 9×9.

Solving strategy

  • Complete near-full units. A row, column or box with three digits gives the fourth for free.
  • Scan for a missing digit. Pick a digit and find the one cell in a box it can legally go.
  • Chain the forced moves. Each placement usually forces the next — follow the cascade.
  • Use it to start young solvers. Master the 4×4 before moving up in size.

Common mistakes

  • Using digits above 4. Only 1–4 appear on a 4×4 grid.
  • Forgetting the box. Each 2×2 box needs 1–4 too, not just the rows and columns.
  • Rushing past a forced cell. Even here, fill the certain cells before guessing anything.
  • Thinking it is too simple to teach. The scanning habit learned on a 4×4 is exactly what larger grids need.

Can I play it here?

Not yet — Sudoku 4×4 isn't one of the puzzle types SudokuStreak generates for now. But you can learn its rules above, and there's plenty here to sink your teeth into meanwhile: