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.
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:
- Try the closely related Classic, which you can play right now.
- Browse all the Sudoku variants we do offer.
- Or print free puzzles from the printable PDF page.
Where to play it
Sudoku 4×4 belongs to the size variant family and runs on 4×4. It is not one SudokuStreak generates yet - but the deduction it trains is the deduction every Sudoku runs on.
Difficulty and type are two separate dials here: the type sets the extra rule, the level sets how much of the grid you start with. Expert Sudoku leaves 25 of the 81 cells filled, where the beginner tools dry up almost entirely; Evil Sudoku leaves 23, with no easy moves at all. Take it at the gentler end while the pattern is still new, and move up once it stops being a fight.