Sudoku Generator

Printable sudoku for every level: 4×4 and 6×6 grids for young solvers and classic 9×9 in three difficulties. Every puzzle has exactly one solution, checked by a solver before you see it.

Grid
Difficulty

Solve the first puzzle on screen: type digits into the empty squares.

Sudoku 9×9 · easy

Name ____________________ Date ________

Fill every row, column and 3×3 box with the digits 1 to 9, each exactly once.

Solutions

How to solve a sudoku: two techniques to teach first

  1. Only one place (hidden single). Pick a digit and a box. Cross out every row and column where that digit already appears. If only one empty square in the box is left, the digit goes there.
  2. Only one digit (naked single). Pick a square. List the digits already in its row, column and box. If just one digit is missing from all three, that is the answer.
  3. Repeat. Every filled square gives new information. Easy puzzles can be finished with these two moves alone; harder ones need pencil marks.

Sudoku in the classroom

Sudoku involves no arithmetic at all; the digits could be letters or colours. What it trains is logical deduction: "this square can't be a 3 because…". Asking students to explain one move out loud to a partner is an easy way to practise reasoning vocabulary. The 4×4 version, using pictures or colours, works even before children know their numbers well.

What makes a sudoku "proper"?

Tap squares to remove (or restore) clues from this solved 4×4. The counter shows how many completed grids still fit. Once it passes 1, the puzzle can't be solved by logic alone: the solver would have to guess.

16 clues left · 1 solution: still a proper puzzle.

The generator does this automatically: it removes clues in random order and puts back any whose removal allows a second solution. For a 9×9, the fewest clues a proper puzzle can have is 17 (McGuire, Tugemann and Civario proved it by exhaustive computer search in 2012).

Questions teachers ask

Does every sudoku have exactly one solution?

Yes. After each clue is removed, a solver counts the solutions; if there would be more than one, the clue goes back. A proper sudoku can always be solved by logic without guessing between two valid answers.

Which size should children start with?

4×4 (digits 1–4, 2×2 boxes) suits ages 5–7 and teaches the core rule in two minutes. 6×6 (2×3 boxes) is a good bridge for ages 7–10. The classic 9×9 comes after that.

What makes a sudoku easy or hard?

Mostly the solving techniques needed, which loosely follow the number of clues. Easy puzzles here keep about half the squares filled; hard puzzles keep around 30%, so solvers need to reason about several constraints at once.

Can I print several sudokus on one page?

Choose 1, 2, 4 or 6 puzzles. They print together on one page with the solutions on the next.

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